Name: Roasted Onions
Prep time: 10 min
Cook time: 50 min
Total time: 60 min
Ingredients: 2 large sweet onions (1½ to 2 pounds); 2 tablespoons melted butter; 1 teaspoon balsamic vinegar; 3 tablespoons water (or broth); ⅛ teaspoon kosher salt (or to taste); ⅛ teaspoon black pepper

Roasted Onions transform humble sweet onions into a buttery, caramelized side with golden edges and plenty of sweet-savory flavor. A little butter and balsamic bring out their natural sweetness, making these tender onions an easy side dish to serve with Air Fryer steak, grilled chicken breasts, or smash burgers.

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Holly’s Recipe Highlights: Roasted Onions

Why Make It: Just a few inexpensive ingredients transform everyday onions into a flavorful, versatile side with very little hands-on cooking.
Technique: Keep the onion rings together in thick slices to help them become tender and caramelized without falling apart.
Tools: A ceramic or glass 9×13-inch baking dish helps the onions cook evenly.

Total Time: 1 Hr (10 Mins Prep) Servings: 4 Cooking Method: Oven

Total Time:: 1 hr
Serves:: 4
Rating:: 4.9/5

Ingredient Notes

sweet onions , butter , vinegar , thyme , salt and pepper with labels to make Roasted Onions.

Sweet Onions: Vidalia, Walla Walla, or another sweet onion gives the mildest, sweetest flavor, while yellow onions also roast well and have a stronger savory taste. Use red onion for a sharper flavor. Cut them into even ½-inch slices, so they cook evenly and finish at roughly the same time.
Seasonings: Add rosemary and thyme sprigs whole across the tops of the onions for a delicate flavor, or chop them finely and sprinkle over the top for more herb flavor.
Water and Broth: Water adds moisture to help the thick onion slices become tender before the edges caramelize, while broth brings a little extra savory flavor.

How to Make Roasted Onions

Cut the onions. Whisk together melted butter and balsamic vinegar (full recipe below).

adding seasonings and vinegar with herbs to onion to make Roasted Onions.

Place the onions in a casserole dish. Add the butter mixture and water, and roast.

Keep the Rings: Leave the slices intact when cutting so the onions soften evenly while maintaining their shape during roasting.
Don’t Overcrowd: A little overlap is fine, but spread the onions out as much as possible so they roast and brown instead of steaming.
For Caramelized Edges: Roast the onions until deeply golden, keeping a close eye on them during the final minutes to prevent over-browning.

Roasted Onions in a dish with one being lifted out with a spatula

Save Every Savory Bite

Keep leftovers in an airtight container in the refrigerator for up to 4 days. Freezing is possible, but thawed onions will be much softer.
Reheat in a covered baking dish in the oven until hot, or microwave individual portions. For crisper edges, reheat uncovered in the oven or air fryer.
Chop the leftovers and stir them into homemade brown gravy for extra sweet-savory flavor, fold them into cream cheese mashed potatoes, or stir them into homemade beef stew near the end of cooking.

More Roasted Vegetable Side Dishes

Brown Sugar Roasted Sweet Potatoes

Easy Oven Roasted Carrots

Roasted Brussels Sprouts

Green Beans Almondine

Did you enjoy this Roasted Onions Recipe? Leave a comment and rating below.

image of Everyday Comfort cookbook by Holly Nilsson of Spend With Pennies plus text

4.86 from 28 votes

Author Holly Nilsson

Roasted Onions

Author Holly Nilsson

Servings 4

Thick slices of sweet onion are brushed with balsamic butter and roasted until tender, golden, and caramelized around the edges.

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Servings 4

Prep Time 10

Cook Time 50

Total Time 1

Ingredients

▢ 2 large sweet onions 1½ to 2 pounds
▢ 2 tablespoons melted butter
▢ 1 teaspoon balsamic vinegar
▢ 3 tablespoons water or broth
▢ ⅛ teaspoon kosher salt or to taste
▢ ⅛ teaspoon black pepper

Instructions

Preheat the oven to 400°F.
Whisk melted butter and balsamic vinegar.
Peel the onions and cut into ½" slices, do not separate the rings.
Place the onions in a greased 9×13 baking dish and brush with the butter mixture.

To get golden, roasted onions instead of steamed ones, spread them out well with minimal overlap.

Pour the water into the casserole dish.
Season with salt and pepper and roast 40 to 50 minutes or until golden and tender.

Notes

Depending on the preference, the material of the baking dish, and the type of onion, cooking can vary. I prefer a ceramic or glass dish and love the little crispy edges.

Check the onions early and roast to your preference.

Leftover roasted onions can be kept in the fridge in a covered container for up to 4 days. They make a great addition to gravy, soup or stew.

4.86 from 28 votes

Nutrition Information

Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.

Course Side Dish

Cuisine American

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