Bring a large pot of salted water to a boil and cook the rigatoni according to package instructions until al dente. Drain and set aside.
Heat a large pot or Dutch oven over medium heat and add the olive oil.
Add the diced onion and sauté until translucent, about 5 minutes.
Add the minced garlic and cook for 1 minute until fragrant.
Remove the Italian sausage from casings and crumble into the pot. Cook until browned and cooked through, about 7-8 minutes.
Add the whole or crushed tomatoes to the pot. If using whole tomatoes, use a blender to blend them to your desired consistency before adding.
Stir in the fresh basil, oregano, red chili flakes, salt, and pepper. Simmer the sauce for 10 minutes to allow flavors to combine.
Reduce heat to low and stir in the heavy cream and grated Parmesan cheese until the sauce is creamy and smooth.
Add the cooked rigatoni pasta to the sauce and gently toss to combine and coat the pasta evenly.
Serve hot, garnished with extra Parmesan cheese or fresh herbs if desired.