Thick caramelized onion slices

I started roasting onion slices the winter I ran out of side dish ideas. One night I sliced a few too thick, tossed them with oil, and forgot about them in the oven. When I remembered, they were golden, soft, and sweeter than anything I'd caramelized on the stovetop. I've been making them this way ever since.

I brought these to a potluck once, thinking they were too simple to impress. Someone asked for the recipe before I even set the tray down. Another person ate three slices standing by the table and later admitted they skipped the main course entirely.

Ingredients

• 2 large yellow onions: Yellow onions hold their shape and turn golden without falling apart, look for firm ones with dry papery skins.
• 2 tbsp olive oil: Just enough to coat each slice and help the edges crisp up without making them greasy.
• 1 tsp sea salt: Draws out moisture and deepens the natural sweetness as they roast.
• ½ tsp freshly ground black pepper: Adds a gentle bite that balances the caramelized flavor.
• ½ tsp dried thyme (optional): I started adding this after smelling it in a friends kitchen, it gives the onions a subtle earthy note.
• 1 tbsp chopped fresh parsley (optional): A bright finish that makes them look intentional on the plate.

Instructions

Prep the oven and pan:

Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. This keeps cleanup easy and prevents sticking.

Slice the onions:

Peel the onions and cut them into ½-inch thick rounds, keeping the rings together as best you can. Dont worry if a few fall apart, they still roast beautifully.

Arrange and season:

Lay the slices flat on the baking sheet in a single layer. Drizzle olive oil over each one, then sprinkle with salt, pepper, and thyme if youre using it.

Roast until golden:

Slide the pan into the oven and roast for 30 to 35 minutes, flipping the slices halfway through. Theyre done when the edges are deep golden and the centers are soft.

Garnish and serve:

Transfer the onions to a serving platter and scatter fresh parsley on top if you like. Serve them warm while theyre still tender and fragrant.

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The first time I made these for my neighbor, she told me she hadnt liked onions since childhood. She finished two slices and asked if I had more. Now she makes them every Sunday and says they changed her mind about vegetables in general.

Choosing Your Onions

Yellow onions are my go-to because they caramelize evenly and hold their shape, but red onions turn jammy and sweet if you want a deeper color. Sweet onions like Vidalia or Walla Walla roast faster and taste almost candy-like, though they can fall apart more easily. Pick onions that feel heavy and firm with no soft spots near the root.

Serving Suggestions

These onions work as a side dish next to roasted chicken or steak, but Ive also layered them into grilled cheese, piled them on grain bowls, and tucked them into wraps with hummus and greens. One friend uses them as a pizza topping, another chops them up and stirs them into scrambled eggs. Theyre the kind of thing that makes leftovers feel like a head start.

Getting Extra Caramelization

If you want deeper color and crispier edges, turn on the broiler for the last 2 to 3 minutes of roasting. Watch them closely because they can go from golden to charred in less than a minute. I keep the oven door cracked and check every 30 seconds until I see the edges darken just enough.

• Use a light-colored baking sheet so you can see how quickly theyre browning underneath.
• Space the slices apart so steam can escape and the edges crisp up instead of steaming.
• Brush them with a little balsamic vinegar in the last 5 minutes for a tangy glaze that clings to the onions.

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These onions remind me that the simplest recipes often become the ones I make most often. I hope they find a regular spot in your kitchen too.

Questions & Answers About the Recipe

→ What type of onions work best?

Yellow onions are ideal for roasting due to their balanced sweetness and structure, but red or sweet onions can add unique flavors.

→ How do I achieve even caramelization?

Flip the onion slices halfway through roasting to ensure both sides turn golden and tender.

→ Can I add herbs to enhance flavor?

Yes, dried thyme or fresh herbs like parsley can be added for an aromatic touch.

→ Is it necessary to keep the onion rings intact?

Maintaining ring integrity helps the slices hold shape and roast evenly, preventing them from falling apart.

→ What dishes pair well with these roasted onions?

They complement burgers, salads, or serve as a savory side to various meals.

→ Can I broil the onions for extra caramelization?

Broiling for 2–3 minutes at the end intensifies browning and deepens flavor, but watch closely to avoid burning.