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Home » Vegetable Recipes » Roasted Onions

Roasted Onions

A photo of Vered DeLeeuw.
by Vered DeLeeuwUpdated Mar 16, 2025
4 Comments
5 from 19 votes

Jump to Recipe Review Recipe

These roasted onions are flavorful and caramelized. They're the perfect side dish or topping for meat and poultry. Even if you're not a fan of onions in their raw state, I think you will love them oven-baked. They are mellow and sweet.

Roasted onions are served on a white plate.

These roasted onions are easy to make, and they are so delicious. They are also versatile - you can use them to top steaks and burgers or as a savory side dish. Raw onions are sharp, but something magical happens when you cook them. They become creamy and mild, almost sweet. It's true for baked onions, sauteed onions, and caramelized onions.

Ingredients

The ingredients needed to roast onions.

See the recipe card for exact measurements. Here are my comments on the ingredients.

  • Medium onions: White or yellow onions work well in this recipe (here's the difference between onion types), although I usually use yellow ones. You can also use red onions in this recipe, or check out this recipe for roasted red onions.
  • Butter: I use plenty of butter - two tablespoons per medium onion, plus more for the pan. The butter greatly enhances this dish.
  • Kosher salt: I use Diamond Crystal kosher salt, by far my favorite salt to cook with.

Variations

  1. Since onions are inherently flavorful, I don't usually add any other seasonings. But if you'd like, you can season them with garlic powder and oregano, using ¼ teaspoon of each. You can also sprinkle them with freshly ground black pepper, as shown in the photo below.
  2. After flipping, you can sprinkle the onions with two tablespoons of grated Parmesan cheese.
  3. You can coat the onions with extra-virgin olive oil instead of butter. In the photo below, I used olive oil with excellent results.
The onions were arranged in a pan.

Instructions

The detailed instructions and step-by-step photos are included in the recipe card. Here's a quick overview.

Peel the onions, slice off their edges, and cut them into five ¼-inch slices. Place the onion slices in a well-buttered, rimmed baking dish. Coat them with melted butter and sprinkle them with salt.

Pouring melted butter on the onions.

Bake the onions until golden brown. This should take about 40 minutes in a 400°F oven. Flip the slices midway through baking.

Flipping the onions.

Serve immediately. Aren't they gorgeous? I wish you could smell them! They smell so good.

The roasted onions are ready.

5 stars rating. Like onion rings without the breading, and MUCH less work! I oven-roasted a sheet pan of several different vegetables to go into a casserole that I planned to make. Had my husband (big onion rings fan) try one of these onion slices, and he wanted to eat them all (and did)!
Home Cook
Read more comments

Recipe Tips

  1. Keep a close eye on the onions during the last ten minutes of baking to make sure they don't burn. Your oven might run hotter than mine. Their edges should be dark brown, not black.
  2. You can double this recipe, roast two onions, and use a 9 X 13-inch Pyrex pan or a parchment-lined rimmed baking sheet.
  3. Don't be afraid to use these as a side dish! They resemble onion rings. We tend to use onions as an ingredient in other recipes, but in this case, they make a delicious side dish.

Serving Suggestions

Roasted onions pair well with meat and poultry. Since I bake them in a 400°F oven, I like to serve them with a main dish I can cook in the same oven. So, among other choices, I often serve them with baked pork chops, baked meatballs, or beef tenderloin roast.

They also make the perfect topping for hamburgers and steaks, including broiled hamburgers, turkey burgers, bison burgers, tri-tip roast, New York strip steak, and ribeye steak.

Storing and Using the Leftovers

You can keep the leftovers in a sealed container in the fridge for 3-4 days. Reheat them, covered, in the microwave at 50% power.

Alternatively, chop the leftovers and mix them into an omelet or a scramble, such as spinach and egg scramble, fluffy scrambled eggs, or egg white omelet. The photo below shows a scramble made with the leftover onions and served with avocado.

A scramble made with leftover onions and served with avocado.

Recipe Card

Roasted onions are served on a white plate.
5 from 19 votes
Save this RecipeSaved! Rate this Recipe Print Recipe

Buttery Roasted Onions

These roasted onions are wonderfully flavorful and caramelized. They're the perfect side dish or topping for meat and poultry dishes.
Prep Time15 minutes mins
Cook Time40 minutes mins
Total Time55 minutes mins
Course: Side Dish
Cuisine: American
Servings: 2 servings
Calories: 123kcal
Author: Vered DeLeeuw
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Video

Ingredients

  • 2 tablespoons butter - plus more for the pan
  • 1 medium onion
  • ½ teaspoon Diamond Crystal kosher salt - or ¼ teaspoon of any other salt, including Morton kosher salt

Instructions

  • Preheat the oven to 400°F. Grease a square 8-inch Pyrex baking dish with butter.
    A buttered baking dish.
  • Peel the onion and slice it into ¼-inch-thick slices. You should get five slices.
    Slicing an onion on a cutting board.
  • Arrange the slices in a single layer in the prepared baking dish. Melt the butter and pour it over the onions. Sprinkle them with kosher salt.
    Pouring melted butter on the onions.
  • Roast the onions until the bottoms are golden, about 20 minutes.
    Placing the onions in the oven.
  • Turn the onion slices to the other side and bake them until golde brown, about 20 more minutes.
    Flipping the onions.
  • Serve immediately.
    The roasted onions are ready.

Notes

  • You can double this recipe and use a 9 X 13-inch Pyrex pan or a parchment-lined rimmed baking sheet.
  • Keep a close eye on the onions during the last 10 minutes of baking to make sure they don't burn. Your oven might run hotter than mine. Their edges should be deep brown, not black. 
  • Since the onions are so flavorful, I don't add any other seasonings. But if you'd like, you can season the onions with garlic powder and oregano, using ¼ teaspoon of each. You can also sprinkle them with grated Parmesan cheese after flipping them. 
  • You can keep the leftovers in a sealed container in the fridge for 3-4 days. Reheat them, covered, in the microwave at 50% power. Alternatively, chop the leftovers and mix them into an omelet or a scramble.

Nutrition per Serving

Serving: 0.5 recipe | Calories: 123 kcal | Carbohydrates: 5 g | Protein: 1.7 g | Fat: 11 g | Saturated Fat: 7 g | Sodium: 363 mg | Fiber: 1 g | Sugar: 2 g

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Comments

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    Recipe Rating




  1. Home Cook says

    February 17, 2025 at 8:33 am

    5 stars
    Like onion rings without the breading, and MUCH less work! I oven-roasted a sheet-pan of several different vegetables to go into a casserole that I planned to make. Had my husband (big onion-rings fan) try one of these onion slices, and he wanted to eat them all (and did)!

    Reply
    • Vered DeLeeuw says

      February 17, 2025 at 8:58 am

      I'm so glad this was a success! Thank you very much for taking the time to write a review. I appreciate it.

  2. Amanda says

    June 15, 2024 at 9:12 pm

    5 stars
    Easy and delicious. Perfect for burgers. I like to mix the leftover into mashed potatoes. Yum!

    Reply
    • Vered DeLeeuw says

      June 16, 2024 at 11:38 am

      I'm glad you liked this recipe, Amanda! Thanks for the comment.

A photo of Vered DeLeeuw.

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Healthy Recipes Blog was founded in 2011 by Vered DeLeeuw. It features real food recipes with a focus on low-carb and gluten-free ingredients. All recipes are nutritionally reviewed by a Registered Dietitian. Contact us at HealthyRecipesBlog@gmail.com.

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