Whole roasted onions are soft, aromatic, and so delicious that they become a stand-alone side dish! This recipe and these tips will give you the perfect baked onion every single time.
Here’s how this is going to go down, my friends: whole roasted onions, roasted with olive oil and butter, roasted with rosemary, roasted whole, roasted to sweet submission.
It’s cold. I mean… really cold. Here’s our chance to crank up the oven, throw these onions inside and lean against the oven door as they transform from sharp and bitey to soft and sweet! And while we’re at it, here’s how to roast any vegetable.
Oh, wait… you might be one of those people who think they don’t like onions. I’m here to tell you that you’re wrong. You exclusively like whole roasted onions, especially these.
And, if you’re feeling fancy, you might want to try this recipe for Ottolenghi’s Miso Butter Roasted Onions and Garlic! It’s like a savory onion candy.
10/10 recommend!
What are roasted onions?
This recipe is just like it sounds. You season and bake whole onions with slices of real butter on top. Roasting them softens the onions and brings out their natural sweetness.
If you aren’t a fan of the sharp flavor of onions, roasting them cuts the boldness back and makes them easier on your palette. And the butter, well… what doesn’t butter do?
Best types of onions to bake
When it comes to roasting or baking onions, use:
- White onions
- Yellow onions
They hold their shape and texture the best. Plus, both types have a strong flavor that sweetens magnificently when you bake them.
The best tips for making oven-roasted onions
The best thing about cooking is how much control you have over the way your food turns out! If you change my recipe, let me know. I’d love to hear what you did (and who knows… maybe I’ll try it that way?).
- Quarter or slice the onions first. The smaller the onions are, the quicker they will bake, so keep an eye on the oven. It will also allow the butter and seasonings to go deep into the onion and become even MORE flavorful.
- Fresh rosemary is the best herb to roast with onions, but try it with fresh sprigs of thyme. Its sweet earthiness can really bring out the buttery notes in the onions.
- Drizzle balsamic vinegar on top of the onions right before you bake them. As the onions caramelize, the vinegar will break the onions down even more and release more sugar (what more could you want?), giving you tangy-sweet onions in the end.
How to roast an onion in the air fryer
Roasting is magic. It’s as simple as that, but you don’t have to heat up the entire kitchen just to roast a few onions (I’m looking at you, summertime humidity).
To roast onions in the air fryer, follow the same instructions in the recipe card!
Place the onions in the air fryer basket. Set it to 375ยฐF and air fry them for 20 minutes. If they aren’t done to your liking, roast for another 10 minutes.
Serve and enjoy
These roasted onions – tops removed and toasted in their jackets – become soft, smooth, sweet, and almost spreadable.
The best way to eat a roasted onion is to slice it and eat it as a side dish along with a juicy pork chop and some fluffy mashed potatoes. Or, you could roast the onions and add a few slices on top of some baked sweet potatoes or on top of your favorite salad for a healthier option – if you’re a fan of that kind of thing.
How to store leftovers
Honestly, whole roasted onions taste the best when they are fresh out of the oven. You can store leftovers in an airtight container in the refrigerator for up to three days.
Just know that they will become softer, and their flavor will change. It just isn’t the same. Eat them fresh, trust me!
I hope you enjoy this recipe. Leave me a comment down below on how you plan to serve these roasted onions. I wanna know!
You might also enjoy these Miso Butter Roasted Onions!
Print
Whole Roasted Onions
- Prep Time: 10
- Cook Time: 45
- Total Time: 55 minutes
Ingredients
- 9 small and medium yellow onions
- 1/4 cup olive oil
- 2 tablespoons unsalted butter, thinly sliced
- coarse sea salt
- fresh cracked black pepper
- fresh rosemary sprigs
Instructions
- Place a rack in the upper third of the oven and preheat oven to 375 degrees F.
- Cut the tops off of each onion, but leave most of the skins on the onion.
- Arrange the onions in a square baking dish or a rimmed sheet pan.
- Drizzle the olive oil over the onions. Place a thin pat of butter on each onion.
- Sprinkle generously with salt and pepper and top with a rosemary sprig.
- Bake for 25 minutes until bubbling and tender.
- Increase the oven temperature to 400 degrees F and cook for another 15 to 20 minutes until the onions are completely tender and the tops are browned.
- Remove from the oven and allow to cool slightly.
- Remove the skins, slice and enjoy warm.
102 Responses
I was intrigued by your suggestion, but in the end decided it was too tedious. So I ended up making as written. Good thing they are still delicious this way. I did not leave the jackets on. Really loved the extra browning. Will make regularly now.
Roast two small, put in blender with garlic clove put chops on top of sauce
Great recipe Joy ?
Baked onions and carrots are my favourite thing. Your onions are also delicious as a chilled snack, very refreshing and safe to take into the scrub for a day with boiled eggs. Iโve only ever made them with cloves.
Thank you for your yummy recipe
Baking them right now, amazing aromaโฆโฆ.but should I have them covered in the oven?
I have a question- do I have to leave the skins on? Iโd. rather remove them first so when they come out of the oven I donโt have to mess around with them, I could just serve them up
I just made them without skins and they were lovely , used thyme instead of rosemary as was using that for another accompanied dish
Cooking these right now. For those with alternative ideas, maybe they could post their own recipes. This one is fine the way it is.
When I try this recipe I might add a little Cajun seasoning.AlsoI thinking about using one of these onions with a baked Potato. Yum?
I made this tonight with both yellow and red onions. I forgot to put my rosemary sprig on. I still really enjoyed it! Thanks!
Iโm making these again tonight!
I am an avid cook now in my mid 70s and have never ever posted a review before. BUT the results of this method of serving onions is mind boggling!!!!
Made this last night for dinner. Holy moly! Not only was the result absolutely incredible, but what a fantastic and extremely easy way to use up a large amount of onions before they go bad. I think this would be a great recipe to make on a Sunday and use for the rest of the week in other recipes. The next time I make it, I might try adding a little balsamic to the tops as well for added sweetness. Iโm just so thrilled I found this recipe!
I loved this recipe. Roasted them tonight for just a little over the suggested baking time and they turned out absolutely delicious.
Such an easy and effective way to cook onions.
This recipe is going to become a regular whenever I cook a roast.
Thank you so much :-)
Great post! It is easy and detailed to follow. Thanks!
Drop the Oil and Salt and lovely snack
Great suggestions for use. Thanks!
This is fabulous….but that pan looks like a nightmare to clean…I think I’ll slip some parchment underneath when I try this…
This recipe looks amazing! Iโm so excited to try it.What would be something good to serve with this?
Someone suggested thinly sliced pork chops with the silky onions. Butter and EVOO oh my!
A question, please – do you leave the root end intact or cut that off when you cut off the tops ?
I leave the root end intact and remove the root end and skin after baking.
The best part about this recipe (and doing it while I write) is *no peeling of the onions*. Gold, right there, let alone all the rest of the goodness!
These were very good but took a LOT longer to cook than the recipe called for. I used the smallest onions I had but they were still likely bigger. I’d say it took at least an hour and 15 minutes and could have used a bit more.
Yes, the longer bake time sounds much better. Thought of that when reading it over. Melted onions. Yum.
Awesome, thanks for jump starting supper for me tonight! I often roast several onions along with whatever root veg I have on hand and I am always surprised (why???) at how well everyone loves them. I’ve combined red and white/yellow/brown onions or shallots with regular Yukon gold potatoes AND sweet potatoes, hard squashes, carrots, parsnips, and towards the end I toss in Brussels sprouts cleaved in two. Isn’t it amazing what a little olive oil, butter and herbs/spices can do? Even better with a rib-eye steak but not required. Stay warm everyone!
We love vegetable suppers. We love baked sweet potatoes and then I’ll add a small yellow onion to go along with each serving that bakes with the potatoes the last 30 to 40 minutes. A healthy filling and easy clean up evening.
This was fun. I neither cut the onions nor baked at the second temperature, but peeled off the dry skin and baked at 375 for about an hour and a half. I laid them out with the roots sticking up which created layers the rose from the onion looking like a meat thermometer that pops up. Effortless.
the print option on your recipes is AMAZING – so easy
Try roasting this recipe on a BBQ. Oh, so yummy!
Tried this today…took twice as long as suggested.
I tried this with large red onions. They were still basically raw after all that time in the oven. My chef instincts told me to cover the pan with foil. Maybe they’ll finish off well now that the foil is on.
So bomb!!
Awesome post :D!
Scoop out the center (use a small paring knife and be careful) and chop the removed onion. Fry it up with some bacon and garlic. Stuff mixture back into the center of the onion, drizzle with olive oil….. then roast them.
You’re welcome.
Hey I tried this and it was awesome, but I was definitely expecting it to be softer, esp. because I ended up cooking it a good twenty minutes longer than called for. I left the butter pat off because I’m dairy free. Is there anything I can do to help this carmelize better?
I just made these and they were amazing! i only made one though and devoured it for lunch, i have an onion obsession an this was perfect.
My Dad used to season them similarly, wrap them in foil and throw them on the grill when he did steaks – he’d keep them on for a while before he threw the steaks on. Delicious on top of that grilled steak and over a the baked potato!
I tried making something very similar a while ago (didn’t know other people did, I just thought I was the nutty onion lover) after reading a recipe in Game of Thrones oddly enough. It mentions one of the characters eating a roasted onion covered in gravy. So while I wouldn’t suggest you cover all of your onions in gravy and potentially ruin them, next time you pair them with a meat that involved gravy maybe take a small slice and give it a little dip, see how it tastes? With just a small slice there isn’t much to lose!
For some reason when I made them (idk if this is the norm)… well I expected the onions to taste like sauteed onions, just large and maybe just a BIT sweeter, but they tasted ridiculously sweet (their taste reminded me of how sweet air smells). Is this the norm? I didn’t have a recipe and used primarily butter instead of olive oil, would the butter make it more sweet than the oil?
Ugh! Comments are only food blog groupies, no one has actually tried this? Who are the people out there commenting on these things that it “looks/sounds so good” or “can’t wait to try it”? Are you all just people trying to redirect attention to your own food blogs?
Can’t wait for someone to try it…sounds amazing…
they do freeze beautifully! theres 4 of us I made a whole tray full and froze them in 4s, reheated in oven after defrosting and delicious. perfect for a huge sack. I also slice about 5 kg and put them in the slow cooker for a day with butter olive oil and black pepper then portion them up to freeze. caramalised onions whenever I need them
I Wonder if they’d freeze?
i don’t think so.
try boiling them, taking off skins, cut in half placein dish cover with heavy cream and parmesan cheese then bake .wow
Trim a little bit off the root end so that you have a flat spot for them to sit level. After you brown them on the top, flip them over for the bottom to brown, as the browned parts are the very sweetest.
You truly are a master at living.
Oh I bet this would make the best garlic-y onion bread!! Roasted onion and garlic.. Holy moly! Thank you for sharing this idea and kicking my imagination into gear! I love some of the other commenter’s ideas too! Baked potatoes! NICE.
Oh I love roasted onions so much! I’ve never tried to add butter, next time I’ll do!
https://justsem.wordpress.com/
I’ve never done this before! It looks amazing. Will give this a shot soon!
I second the comment for wanting to know how you cook thin pork chops without them tasting over dry! Pretty please tell us??
Quickly fry them on a high heat with some oil. Colour both sides then, take off the heat, cover in foil and stand for a couple of minutes to finish cooking without burning. If they were fatter pork steaks, I’d do the same but put in the oven at around 150C to finish cooking.
yumm! just baked at 30 minutes at 375 and 50 minutes at 400, could have used more time but i was impatient : )
Ha! I love these onions! I make them every year for Thanksgiving! Somehow I always improve them and this year it is going to be by keeping the skins on in 2015!
Below is my version.
https://trenchdesign.blogspot.com/2009/11/mt-tabor-onions.html
I love it when you post a recipe I have all the ingredients for on hand AND it fits into my pre-existing dinner plan.
They tasted like roasted onions you might have had in a root vegetable medly. I was hoping they would become creamier than normal roasted onions, more like roasted garlic, but alas no. They were pretty.
Also I was impatient and they were too hot to slice thin, so I just cut one in half and put it on the dinner plate with some coleslaw, roasted butternut and hamburgers. I roasted the onions in the same oven as the squash so they were easy to make.
Whole Roasted Onions were not bad, but not as special as they look. #my2cents
Made these for dinner last night (served them with sausage, etc.) Very yummy. Will make again!
This post made me laugh out loud, and my mouth water. Pork and onions is ALWAYS a winning combo!
Tried them last night with my beef roast. Wonderful.
https://cookingmania.yuku.com
Brilliant! I can’t wait to try this. Roasting = perfection.
I’m a ONION LoVER and I’ve never tried making whole roasted onions. Brilliancy at it’s best. These have got to be amazing. Onions are one of my favorite parts of roasted veggies.
Hope you had a wonderful weekend Joy!
I ran out of onions for a brief and terrible time last week. Do you know what I thought about the whole time? ONIONS. Onions are SO good for you that native Americans used to very jealously guard and claim wild onion fields for their own. They believed that onions were a sort of potent medicine. THIS recipe looks awesome, by the way!
My sister introduced me to onion bombs – take an onion like this, top with butter and a beef buillion cube, wrap in aluminum foil and grill. AMAZING. Can’t wait to try this indoor version!
No need to roast onions separately. They cook well in their skins ,tucked in – normally one per person – with any roast joint/chicken/ potatoes.Put in about half an hour to forty-five minutes (depending on size) before the end of cooking. If your chicken for example has produced a lot of juice,better to pour some off before adding the onions,so they don’t stew.
Fabulous! I’ve never done this and it is so happening this week. :)
Looks delicious.
How hard was it to clean that roasting dish afterward? Just curious :)
I love this joy! you are the best :)
Oh my goodness! That’s definitely an accompaniment to tonight’s dinner! Yummy sweet onion, sounds delicious!
clementinebuttercup.blogspot.co.uk
Wow, those look delicious! We’ve done something similar with garlic but would never think to try this with onions. What vegetarian pairings would this work with?
These are the last three days in my mother’s kitchen in Germany and I have some onions left. What a good idea to use them. I just have to figure out what to serve with them, maybe some Rouladen ( rolled beef, stuffed with bacon and pickles) .
I’m a fan of onions, but I’ve never thought of roasting them whole, with their skin still on. And this is great for me because I hate peeling onions.
I cannot wait to try this! I roast lots of veggies but have never thought of this. They look amazing! Love your photos!
I’m making this right now, and the whole house smells so delicious! I can hardly wait to shamelessly stuff my face with these.
These are perfection! I love the simplicity of this recipe. I could probably eat 3 of those onions in oe sitting.
WOW. Yum. My husband hates onions so I’d never get away with this. But based on your photos, oh how I wish I could! They look amazinggg!
No, no, no! Ok, they do look nice, possibly they are delicious (for some people) but I am an anti- onion person and eating them whole like that would be a cruel thing to do (to myself)! :)
I don’t think I’ve found a veggie yet that didn’t taste better after a roasting. This is just another wonderful example of that fact.
https://cookingmania.yuku.com
Can I come eat at your house?
Love this! Another neat way is to slice them thick and lay them flat on a cookie sheet, drizzle with olive oil and balsamic vinegar and throw them under the broiler! You can just eat them all by themselves in that tangy goodness!
Yummy!
I love onions so I’m totally down to try this!
I love onions so I’m certainly down to try this!
All of a sudden I’m veeeeeeery glad I bought the 10 pounder bag of onions at Costco this week. ;)
Those look delicious! Is there a magic trick you use to clean the bottom of your dish? I love roasted veggies but hate the mess left behind :(
This looks simple and delicious!
https://addalittlefood.com
I do this with garlic but never thought to try onions! Great idea.
Of course! Leave those lovely papery skins on. Sort of a why-didn’t-I-think-of-that (?) kind of thing (but I never do). The real question is how you cook thin pork chops without creating small leathery bits of horror.
Ahhh, these look amazing!! I’ve roasted onions with other veggies before, but never whole onions! I must try!!
I cook at least one onion per day for the two of us, and now I will have another way to feature them! I will toss in some carrots and potatoes alongside, and that will be the highlight of tonight’s dinner! Healthy and so delish!
Given how much I love onions, how have I never thought of this before?? Guess what I’m making this weekend!
xx Kathryn
https://www.throughthethicket.ca
Yes! Roasting vegetables is one of my favourite things to do. Definitely trying these soon!
Yum this entire post just made me drool, and it’s not even noon yet! I love roasted onions, they are so yummy. Thanks for the easy to follow recipe!
Looks like your onions fit well in the pan. If they do not, would you recommend using a little aluminum foil as spacers to get them all to stand up? Also, my wife likes sweet onions. Any modification needed if I use sweet onions other then probably fewer fit into the pan?
Looking forward to trying this one.
I’ve never given much thought to roasting whole onions! Adding rosemary and butter sound like just the trick.
Brilliant! Brilliant! Brilliant! These would go with so many things.
I absolutely love roasted and caramelized onions. It is when they’re in their most perfect state!
You’re right — roasting IS magic! Brussel sprouts! Cauliflower! And now onions. Can’t wait to try.
Roasted onions are a favorite in my house.
my father used to drop whole onions in my great grandmother’s simmering marinara sauce pot because he loves them so much. this would blow his mind.
i LOVE onions and these babies look amazing. i can’t wait to try this recipe out! *swoon*
I am a big fan of onions, and I love how simple it is. Though I imagine it might be difficult to pair with anything other than meat?
They would go with lots of veggie things: nut loaf, fritatta, with a big lump of cheddar and some crusty bread, or sliced onto a pizza base would be good too, with tomatoes, mozzarella and basil. Yum!
Thank you so much! This recipe sounds delicious and I will immediately prepare them this evening to the baked potatoes and the Bavarian meat loaf I planned already to cook :)
xx from Bavaria/Germany, Rena http://www.dressedwithsoul.com
Saving this! We are an onion loving family and this looks perfect :)