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    Home » Vegetable Recipes » Roasted Onions

    Roasted Onions

    Last updated: Jan 15, 2023 · Recipes developed by Vered DeLeeuw and nutritionally reviewed by Rachel Benight MS, RD · This website generates income via ads and uses cookies.

    Jump to Recipe Card

    Roasted onions are wonderfully flavorful and caramelized. They make a wonderful side dish or topping for many different meat and poultry dishes.

    Even if you're not a fan of them in their raw state (I'm not), I think you will love them oven-baked. They are mellow and sweet.

    Roasted onions served on a white plate with a red napkin.

    Raw onions are quite sharp. I tend to avoid them. But something magical happens when you cook them. They become creamy and mild, almost sweet.

    Baking onions in the oven makes them tender, browned, and very flavorful. This is a recipe that I like to make because it's truly easy, yet it produces delicious results.

    It's also a very versatile recipe - you can use the roasted onions as a topping or even as a side dish all on its own.

    Jump to:
    • Ingredients
    • Instructions
    • Expert tip
    • Frequently asked questions
    • Variations
    • Serving suggestions
    • Storing leftovers
    • Related recipes
    • Recipe card

    Ingredients

    You'll only need three simple ingredients to make this tasty side dish. The exact measurements are included in the recipe card below. Here's an overview of what you'll need:

    • Medium onions: White or yellow onions work well in this recipe (here's the difference), although I usually tend to use yellow ones.
    • Butter: I use plenty of butter - 2 tablespoons per medium onion plus more for the pan. The butter adds wonderful flavor to the dish. Another tasty option would be to use olive oil. But personally, I prefer butter.
    • Kosher salt: I use kosher salt in most of my recipes, this one included. If using fine salt (such as sea salt), you might want to use less of it, or the dish could end up too salty.
    The ingredients needed to roast onions.

    Instructions

    It's truly easy to roast onions in the oven. Scroll down to the recipe card for the full details. Here are the basic steps:

    • Your first step is to peel the onions, slice off their edges, then cut them into four or five thick slices, as shown in the video below.
    • Now, place the slices in a well-buttered rimmed baking dish. Coat them with melted butter and sprinkle them with Kosher salt.
    • The last step is to bake the onions until golden brown. This should take about 40 minutes in a 400°F oven, and you should flip the slices midway through baking.
    A four-photo collage showing the steps for roasting onions in the oven.

    Expert tip

    Keep a close eye on the onions during the last 10 minutes of baking to ensure they don't burn. Your oven might run hotter than mine.

    Frequently asked questions

    Is this a topping or a side dish?

    We don't often think about onions as a separate side dish. We tend to use them as an ingredient in other recipes. But in this case, they do make a wonderful, very flavorful side dish.

    Why do onions become sweet when they're cooked?

    Onions contain a relatively large amount of sugar. During the cooking process, large sugar molecules are broken down into smaller ones and those have a sweet taste.

    Are yellow and white onions interchangeable?

    White onions are sweeter and milder than yellow ones. They're not as pungent when served raw. I wouldn't use yellow onions in a recipe that calls for raw white ones. But if a recipe calls for cooking yellow onions, it's fine to use white onions instead.

    Variations

    Since the onions themselves are so flavorful, I don't usually add any other seasonings. But if you'd like, you can season them with garlic powder and oregano. You can also sprinkle them with grated parmesan cheese after the first 20 minutes of cooking.

    Serving suggestions

    This lovely side dish goes really well with meat and poultry dishes. Since I bake it in a 400°F oven, I like to serve it with a main dish that I can cook in the same oven. It's just so convenient!

    So, among other choices, I often serve roasted onions with baked pork chops, with baked meatballs, or with beef tenderloin roast. They also make a wonderful topping for hamburgers, such as these broiled hamburgers.

    Storing leftovers

    Leftovers keep quite well in the fridge, in a sealed container, for 3-4 days. Reheat them, covered, in the microwave on 50% power. Leftovers are also very good when chopped and mixed into an omelet or a scramble such as this spinach and eggs scramble.

    Baked onions served on a white plate with a red napkin.

    Related recipes

    • Sauteed Onions.
      Sauteed Onions
    • Pickled Red Onions.
      Pickled Red Onions
    • Roasted Garlic Cloves
      Roasted Garlic Cloves
    • Roasted red onions.
      Roasted Red Onions

    👩🏻‍🍳 I typically publish a new or an updated recipe once a week. Want these recipes in your inbox? Subscribe! You can unsubscribe at any time.

    Recipe card

    Roasted Onions.
    4.98 from 91 votes
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    Buttery Roasted Onions

    Roasted onions are wonderfully flavorful and caramelized. They make a wonderful side dish or topping for meats and poultry.
    Prep Time15 mins
    Cook Time40 mins
    Total Time55 mins
    Course: Side Dish
    Cuisine: American
    Servings: 2 servings
    Calories: 123kcal
    Author: Vered DeLeeuw
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    INGREDIENTS

    • 2 tablespoons butter plus more for the pan
    • 1 medium onion
    • ½ teaspoon Diamond Crystal kosher salt

    INSTRUCTIONS

    • Preheat your oven to 400 degrees F.
    • Grease a square 8-inch Pyrex baking dish with butter.
    • Peel the onion and slice it into ¼-inch-thick slices, as shown in the video below. You will probably end up with five slices.
    • Arrange the slices in a single layer in the prepared baking dish. Melt the butter and pour it all over the onions. Sprinkle with Kosher salt.
    • Roast the onions until the bottoms are golden, about 20 minutes.
    • Turn the onion slices to the other side and bake them until golden-brown, about 20 more minutes.

    WATCH THE VIDEO:

    NOTES

    You can easily double this recipe and use a 9 X 13 -inch Pyrex pan.
    Keep a close eye on the onions during the last 10 minutes of baking to ensure they don't burn. Your oven might run hotter than mine.
    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. You can also sprinkle them with grated parmesan cheese after the first 20 minutes of cooking.

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    DISCLAIMERSMost of our recipes are low-carb (or keto) and gluten-free, but some are not. Please verify that a recipe fits your needs before using it. Recommended and linked products are not guaranteed to be gluten-free. Nutrition info is approximate and the carb count excludes non-nutritive sweeteners. Nutrition info may contain errors, so please verify it independently. Recipes may contain errors, so please use your common sense when following them. Please read our Terms of Use carefully before using any of our recipes.

    NUTRITION PER SERVING

    Serving: 0.5recipe | Calories: 123kcal | Carbohydrates: 5g | Protein: 0.7g | Fat: 11g | Saturated Fat: 7g | Sodium: 363mg | Fiber: 1g | Sugar: 2g
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    About the Author

    Vered Deleeuw Vered DeLeeuw, LL.M., CNC, has been following a low-carb real-food diet and blogging about it since 2011. She's a Certified Nutrition Coach (NASM-CNC), has taken courses at the Harvard School of Public Health, and has earned a Nutrition and Healthy Living Certificate from Cornell University. Her work has appeared in several major media outlets, including Healthline, HuffPost, Today, Women's Health, Shape, and Country Living. Click to learn more about Vered.

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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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