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 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!
Yes! Roasting vegetables is one of my favourite things to do. Definitely trying these soon!
Sam @ PancakeWarriors
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.
Sammi @Sunshine Recipes
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.
Christina @ The Beautiful Balance
I absolutely love roasted and caramelized onions. It is when they’re in their most perfect state!
Gina @ Vintage Junk in My Trunk
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
Natalie @ The Ravenous Mommy
Saving this! We are an onion loving family and this looks perfect :)