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.
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 375°F 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
- 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
- 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.
I have a question- do I have to leave the skins on? I’d. rather remove them first so when they come out of the oven I don’t 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!
I’m 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. I’m 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! I’m 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.