Instructions

1. Bring a large pot of salted water to a boil.
2. Heat 2 tablespoons of the butter in a large skillet over medium heat. Cook until melted and slightly browned, then add in the thinly sliced onion. Cook until onion is slightly caramelized and golden, about 10 minutes. Add in the brussels sprouts, garlic, thyme, salt and pepper and cook for another 5-10 minutes until brussels sprouts are crispy.
3. While the onion and sprouts are cooking, add in the cavatappi and cook until al dente according to package directions. Drain, reserving 1/2 cup pasta water and set aside.
4. Stir in the lemon zest and juice, parmesan cheese, remaining tablespoon of butter and finely chopped walnuts into the brussels sprouts and add the pasta along with a tablespoon or two of the reserved pasta water. Toss to combine. If the pasta sauce is too thick, add another tablespoon or two of pasta water to thin.
5. Season to taste with salt and pepper and serve immediately.