The 4-Ingredient Side Dish That Wows My Guests Every Time

Melting potatoes (aka fondant potatoes or pommes de terre fondantes) are one of my all-time favorite potato preparations. Being a diehard fan of alliums, after learning that a similar cooking method could be applied to onions, I knew I had to try it.

The so-called “melting” technique refers to onions slow-cooked to the point of becoming really soft with a delicate sweet-savory flavor. Several recipes I found utilize a muffin pan to roast the sliced onions. I personally find cleaning individual muffin cups to be a pain, so I wanted to see if it was possible to achieve similar results with a plain ol’ sheet pan.

The Melting Onions Technique

This sheet pan method consists of three main steps. First, you roast the seasoned sliced onion rings until they are nicely browned on the bottom. Then you pour a mixture of broth and balsamic vinegar into the pan (making sure the liquid doesn’t reach higher than halfway up the onions) and continue roasting. Lastly, after about half of the liquid has evaporated, you gently flip the onions to brown on the other side.

Tips for Flipping the Onions

The only potentially challenging step of this recipe is keeping the onions intact while flipping. The best tool for this job is a small offset spatula: gently slide it under the onions with one hand while supporting the onion with a butter knife on the other side. If you don’t own an offset spatula, you can flip the onions with a butter knife, too. Either way, even if the onions don’t stay in a neat stack, they’ll still be delicious!

Roasty Sides

• Crispy Parmesan Broccoli
• Roasted Brussels Sprouts
• Garlic Roasted Potatoes
• Honey Roasted Carrots With Dates and Hazelnuts
• Roasted Winter Squash With Cilantro Chimichurri

Preheat the oven to 425°F.

Prepare the onions:

Trim the onion ends, then peel and discard the onion skins. Cut the onions through their “equator” into 1/2-inch-thick rings, keeping all the layers intact.

Pour the oil into a rimmed half-sheet pan and place the onions on top. Flip each onion using a thin spatula and rub it in the oil so both cut sides get coated, careful to keep the slices intact. Sprinkle the top-facing side with thyme, salt, and pepper, then flip with a spatula and season the other side. Space the onions evenly apart on the pan.

Roast, part 1:

Roast until the onions are nicely browned on the bottom, about 20 minutes.

Combine the broth and balsamic vinegar in a measuring cup, then pour the liquid into the sheet pan, making sure it doesn’t reach higher than halfway up the onions (you don’t want them swimming in the broth!).

Roast, part 2:

Continue roasting until about half of the liquid has evaporated, about 15 minutes. 

Remove the pan from the oven. Using a small offset spatula (or a butter knife), gently flip the onions, making an effort to keep the onions together. Return the pan to the oven, rotating it 90 degrees, and continue roasting until all liquid has evaporated, about 10 minutes more.

Transfer to a serving platter and serve hot. Store leftover melting onions in an airtight container in the fridge and eat within 2 days.

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