One-Pot French Onion Pasta with Gruyère

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