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Cheesy Roasted Onions

This Cheesy Roasted Onion dish is the perfect blend of sweet, caramelized onions and rich, gooey cheese. Roasting the onions brings out their natural sweetness, which is enhanced by the savory flavors of Gruyère and mozzarella cheese. The crispy panko breadcrumbs add a delightful crunch, making every bite a perfect balance of textures. Finished with a touch of fresh thyme and a hint of sherry vinegar, this dish is a comforting and flavorful side that pairs wonderfully with meats, or can even be enjoyed as a stand-alone appetizer. Whether you’re hosting a dinner party or just treating yourself to something special, these cheesy roasted onions are sure to impress!
Prep Time5 minutes
Cook Time10 minutes
Total Time15 minutes
Course: Lunch
Keyword: Cheesy Roasted Onions
Servings: 8
Calories: 135kcal

Ingredients

  • 2 tablespoons extra-virgin olive oil
  • 2 tablespoons unsalted butter melted (divided)
  • 1 ½ tablespoons fresh thyme chopped (divided)
  • ½ teaspoon salt
  • ½ teaspoon ground pepper
  • 3 large sweet onions 12 oz. each, sliced 1 inch thick
  • ⅓ cup panko breadcrumbs
  • ½ cup low-sodium beef broth
  • 1 tablespoon sherry vinegar or apple cider vinegar
  • ½ cup shredded Gruyère cheese
  • ½ cup shredded mozzarella cheese

Instructions

Prepare the onions for roasting

  • Preheat the oven to 450°F (230°C). Place the oven rack in the upper third position.
  • In a small bowl, mix:
  • 2 tablespoons olive oil
  • 1 tablespoon melted butter
  • 1 tablespoon chopped thyme
  • ½ teaspoon salt and ½ teaspoon pepper
  • Arrange the onion slices in a single layer on a metal baking pan (avoid using glass or ceramic, as they may shatter).
  • Brush the butter mixture evenly over both sides of the onion slices.

Roast the onions

  • Roast for 30 minutes, flipping once halfway, until both sides are golden brown.

Make crispy breadcrumbs

  • In the same bowl, combine:
  • ⅓ cup panko
  • 1 tablespoon melted butter
  • ½ teaspoon chopped thyme
  • Heat a small nonstick skillet over medium-high heat. Toast the panko, stirring occasionally, for 2-3 minutes until golden brown and fragrant. Set aside.

Soften the onions

  • Flip the onions again. Pour in the beef broth and sherry vinegar.
  • Roast for another 10 minutes until the broth slightly reduces and the onions become very soft.

Broil with cheese

  • Set the oven to broil (about 480°F/250°C).
  • Sprinkle the shredded Gruyère and mozzarella evenly over the onions.
  • Broil for about 1 minute until the cheese melts and bubbles.

Garnish and serve

  • Sprinkle the toasted breadcrumbs on top.
  • Garnish with fresh thyme leaves, if desired.
  • Serve with the remaining sauce from the pan.