- 3 tablespoons unsalted butter
- 1 fennel bulb, thinly sliced, plus fronds for serving
- 1 medium onion, thinly sliced
- kosher salt and black pepper
- 16 to 18 ounces fresh or frozen cheese ravioli
- Melt 2 tablespoons of the butter in a large skillet over medium heat.
- Add the fennel, onion, ½ teaspoon salt, and ¼ teaspoon pepper, and cook, stirring occasionally, until tender and golden brown, 25 to 30 minutes.
- Meanwhile, cook the ravioli according to the package directions. Reserve ¼ cup of the pasta water, drain the ravioli, and return them to the pot.
- Gently add in the fennel, reserved pasta water, and remaining tablespoon of butter. Sprinkle with the fennel fronds before serving, if desired.