French Onion Rigatoni with Gruyère in One Skillet

Caramelized onions are the heart of French onion soup, and here they become the base of a skillet pasta. Rigatoni simmers in savory onion broth until tender, then a blanket of Gruyère turns golden and bubbling in the oven. Everything comes together in one cast iron pan, so there is one pot to clean and a dish that tastes like a cozy bistro night.

This French onion rigatoni starts with patient caramelizing. Thinly sliced yellow onions cook slowly in butter until they turn deep golden and jammy, building sweetness and a rich, toasty flavor. Garlic and fresh thyme go in next, followed by broth that lifts every browned bit from the bottom of the pan.

Uncooked rigatoni then goes straight into that savory liquid and simmers until tender, absorbing the flavor of the onions as it cooks. Finally, shredded Gruyère melts into the pasta for a creamy sauce, and a second layer of cheese browns under the broiler. The result is a complete dinner built on classic French onion soup flavors, ready in about an hour from start to finish.

Ingredients

Why this recipe works

Caramelizing onions slowly is what gives this dish its depth. Low heat and regular stirring let the natural sugars in the onions break down and brown gradually, which creates the deep golden color and sweet, savory taste that define French onion soup.

Rushing the process with high heat would scorch the onions before they turn jammy, leaving a bitter edge instead of sweetness.

Cooking the rigatoni directly in the seasoned broth is the second key. Instead of boiling pasta separately and draining it, the rigatoni absorbs the onion and garlic flavors as it simmers, and its starch thickens the remaining liquid into a light sauce.

Adding the cheese off the heat then keeps it melting smoothly rather than turning stringy or grainy, so the sauce stays creamy.

Notes and substitutions

Gruyère is the traditional cheese for French onion soup, and its nutty, slightly sweet flavor melts smoothly. Buy a block and shred it yourself on a box grater, because pre-shredded cheese often contains anti-caking agents that keep it from melting as silky. Comté is a close cousin and works well if Gruyère is hard to find, while Swiss cheese gives a milder result.

A 12-inch cast iron skillet is the best pan for this recipe. It holds heat evenly for the slow onion caramelization, and it goes from stovetop to oven without any transfer.

Use a wooden spoon to scrape the browned bits from the bottom of the pan, since they carry much of the flavor. If you do not have an oven-safe skillet, cook everything in a wide pot and move the mixture to a broiler-safe dish before adding the top layer of cheese.

• Gruyère cheese: Comté or Swiss cheese, shredded the same way
• Beef broth: Vegetable broth for a lighter onion flavor
• Rigatoni pasta: Penne or cavatappi, adding a splash of broth if the pasta looks dry

Equipment

• 12-inch cast iron skillet
• Chef's knife
• Cutting board
• Box grater
• Wooden spoon
• Oven-safe rack