Thick Caramelized Onion Slices

I discovered the magic of roasted onions on a quiet Sunday afternoon when a friend brought them to a potluck, golden and caramelized, sweet enough to eat like candy. The simplicity knocked me back—just onions, oil, and time in the oven. I've been making them ever since, and now they're the first thing people ask for when they know I'm cooking.

I remember making these for my partner's family dinner, nervous about bringing such a humble side. When everyone reached for seconds and thirds, barely touching the other dishes, I realized I'd stumbled onto something special. Since then, they've shown up at nearly every gathering.

Ingredients

• 2 large yellow onions: The foundation of everything—yellow onions have the perfect balance of sweetness and depth when roasted. Don't skip peeling them fresh; it makes a real difference in flavor.
• 2 tbsp olive oil: This is what carries the heat and helps create those caramelized edges. Good quality oil matters here since it's the only fat in the dish.
• 1 tsp sea salt: Draw out the onions' natural sweetness and brings out their best flavor. Taste as you go.
• ½ tsp freshly ground black pepper: Freshly ground is worth the extra second—it adds a gentle bite that balances the sweetness.
• ½ tsp dried thyme (optional): A whisper of thyme adds an earthy note, but honestly, the onions are beautiful on their own too.
• 1 tbsp chopped fresh parsley: Just for garnish and color—a small touch that makes them look like you spent all day cooking.

Instructions

Get your oven ready:

Preheat to 400°F and line your baking sheet with parchment paper. This prevents sticking and makes cleanup almost effortless.

Prepare your onions with care:

Peel them, then slice into ½-inch thick rounds. This thickness is key—thinner slices dry out, thicker ones don't caramelize properly. Keep those rings intact if you can; they're prettier that way and hold together beautifully.

Arrange and season:

Lay the slices flat on your sheet, spacing them so they have a little room to breathe. Drizzle each one generously with olive oil, then sprinkle salt, pepper, and thyme. Don't be shy here.

Let the oven do its magic:

Roast for 30–35 minutes, flipping halfway through. You'll smell them before they're done—that sweet, slightly caramelized aroma is your signal to check on progress. They're ready when the edges turn deep golden and the centers are fork-tender.

Finish with style:

Transfer to a serving platter and scatter fresh parsley over top if you have it. Serve while they're still warm, when they're at their most tender and sweet.

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There's a moment when roasted onions stop being a vegetable and become something more—a flavor that brings people together. I've watched quiet dinner conversations light up when someone tastes how sweet they've become, and seen people who swear they don't like onions ask for the recipe.

Flavor Variations to Explore

The beauty of this recipe is how forgiving it is. Red or sweet onions bring a deeper, earthier sweetness if you want to experiment. Vidalia onions are almost dessert-like when roasted. I've even tried them with a tiny splash of balsamic vinegar drizzled at the end—it adds a sophisticated tang that's lovely for more formal meals.

Ways to Use Your Roasted Onions

Once you make them, you'll find yourself reaching for them constantly. Layer them on sandwiches and burgers where they add sweetness and elegance. Toss them into grain bowls, scatter them over salads, or serve them quietly beside roasted vegetables and grains. They're even wonderful stirred into creamy soups or used as a topping for crostini with goat cheese.

The Oven Timing That Works Every Time

One thing I've learned is that every oven is slightly different—some run hot, others cool. Start checking around the 25-minute mark, looking for golden color and tender flesh. Don't stress if yours take a few minutes longer; the magic happens slowly here. This dish rewards patience with sweetness.

• If your oven runs hot, start checking at 25 minutes to avoid over-browning
• A high-sided baking sheet prevents oil from dripping onto your oven floor
• Parchment paper isn't just for easy cleanup—it helps distribute heat more evenly

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This recipe proved to me that sometimes the most memorable dishes are the simplest ones. Roasted onions are a gentle reminder that good cooking is really just knowing what to do and giving it time to work.

Questions & Answers About the Recipe

→ What type of onions work best for roasting?

Yellow onions are ideal for roasting due to their natural sweetness and firmness, but red or sweet onions provide a different flavor twist.

→ How can I achieve the best caramelization?

Roast the onions at 400°F and flip once halfway through. For deeper caramelization, broil them for 2–3 minutes at the end.

→ Can I add herbs or spices for extra flavor?

Dried thyme is a great optional seasoning. Fresh parsley works well as a garnish to brighten the dish.

→ What dishes pair well with these roasted onions?

They complement burgers, salads, or serve as a tasty side dish to any main course.

→ Are these roasted onion slices suitable for specific diets?

Yes, they are naturally vegan and gluten-free, making them suitable for various dietary preferences.