Bring a large pot of salted water to a rolling boil. Add the rigatoni pasta and cook it according to the package instructions, usually about 10 to 12 minutes, until al dente. Drain and set aside.

In a large skillet, heat over medium heat. Add the Italian sausage and break it apart with a spatula. Cook for 5 to 7 minutes until browned and fully cooked.

Add chopped onions and cook alongside the sausage for 3 to 4 minutes until translucent. Stir in minced garlic and cook for 1 additional minute until fragrant.

Add diced tomatoes and heavy cream to the skillet. Stir to combine and let simmer for 3 to 5 minutes until the sauce thickens slightly.

Gently toss the cooked rigatoni into the skillet, mixing until all pasta is coated with sauce.

Sprinkle grated parmesan cheese and add torn basil leaves. Toss to combine until the cheese melts into the sauce. Serve hot.