One-Pot French Onion Pasta with Gruyère

Deeply browned onions give this cozy pasta its sweet-savory flavor. The onions need time, but the rest comes together in the same pot. Gruyère melts into the starchy cooking liquid for a glossy finish, while a little Dijon keeps the richness balanced.

Prep: 10 minutes · Cook: 50 minutes · Yield: 4 servings

Ingredients

• 2 tablespoons unsalted butter
• 1 tablespoon olive oil
• 3 large yellow onions, thinly sliced
• 1/2 teaspoon kosher salt, plus more to taste
• 3 garlic cloves, minced
• 1 teaspoon fresh thyme leaves, plus more for serving
• 1 tablespoon balsamic vinegar
• 4 cups low-sodium vegetable or beef broth, plus extra as needed
• 12 ounces dry rigatoni
• 1 teaspoon Dijon mustard
• 1 cup freshly grated Gruyère (about 4 ounces)
• Black pepper to taste

How to Make It

1. Heat the butter and oil in a wide heavy pot over medium heat. Add onions and salt. Cook for 30–35 minutes, stirring often, until deeply golden. Lower the heat if they catch; add a tablespoon of water to loosen browned bits as needed.
2. Stir in garlic and thyme for 30 seconds. Add balsamic vinegar and scrape the bottom of the pot. Add broth and bring to a boil.
3. Add rigatoni. Simmer briskly, stirring frequently so it does not stick, for 12–16 minutes or until the pasta is tender. If the pot dries out before the pasta cooks, add hot water or broth 1/4 cup at a time.
4. Take off the heat and stir in Dijon. Let the bubbling settle, then add Gruyère in small handfuls, stirring until melted. Adjust with a splash of hot broth if needed. Taste and finish with black pepper and thyme.

Tips for the Best Result

Caramelize the onions before adding broth; pale onions will produce a milder result. Grate cheese from a block so it melts smoothly. Pasta shapes absorb different amounts of liquid, so use tenderness as the final guide.

Storage and Reheating

Refrigerate covered for up to 3 days. Reheat with a splash of broth over low heat, stirring often, until hot throughout.

Image: AI-generated serving illustration. Cooking times are approximate; use the texture and temperature cues above.