Start by bringing a large pot of salted water to a rolling boil over high heat. Add the rigatoni and cook for 8-10 minutes until al dente.

Reserve about 1 cup of the pasta cooking water in a separate bowl. Drain the remaining water using a colander.

In a large skillet, heat 2 tablespoons of olive oil over medium heat and sauté the diced onion for 4-5 minutes until translucent.

Add the minced garlic and stir for about 1 minute, being careful not to let it burn.

Crumble and add the Italian sausage to the skillet. Cook for 6-8 minutes until well browned.

Pour in the can of diced tomatoes and simmer for about 15 minutes over medium-low heat.

Add ¼ teaspoon of red chili flakes along with salt and pepper to taste. Stir well to combine.

Lower the heat to medium-low and gradually pour in 1 cup of heavy cream, stirring continuously for 5-7 minutes.

Stir in 1 cup of grated Parmesan cheese until melted. Use reserved pasta water to adjust sauce consistency if needed.

Add the drained rigatoni to the skillet and gently toss until each piece is coated with the sauce.

Serve hot, garnished with additional grated Parmesan and fresh basil leaves.