Bring a large pot of salted water to a boil. Add rigatoni and cook according to package instructions until al dente. Drain and set aside.

In a skillet, heat olive oil over medium heat. Add the sausage and cook, breaking it up with a wooden spoon, until browned and cooked through, about 5-7 minutes.

Add chopped onion and garlic to the skillet. Saut? until the onion is translucent, about 3-4 minutes.

Stir in the Swiss chard and cherry tomatoes. Cook until the chard is wilted and the tomatoes are softened, about 5 minutes.

Add the cooked rigatoni to the skillet. Toss everything together, adding red pepper flakes, salt, and black pepper to taste.

Serve hot, topped with grated Parmesan cheese.