Cook the pasta: Bring a large pot of salted water to a rolling boil. Add the rigatoni and cook according to package instructions until just al dente, stirring occasionally to prevent sticking. Reserve a small cup of pasta water before draining, then set the cooked pasta aside.
Brown the sausage and onion: While the pasta cooks, heat a large skillet over medium-high heat. Add the Italian sausage and chopped onion. Use a wooden spoon or spatula to break the sausage into bite-sized crumbles. Sauté for 8–10 minutes until the sausage is browned and fully cooked and the onion is soft and fragrant.
Add garlic for flavor: Stir in the minced garlic and cook for about 1 minute, allowing the garlic to release its aroma without burning.
Build the tomato base: Tilt the skillet slightly and spoon out excess grease, leaving enough to keep the sauce flavorful. Pour in the diced tomatoes and crushed tomatoes, stirring well to combine with the sausage mixture. Lower the heat slightly and let the sauce simmer gently for 10 minutes, stirring occasionally, until it thickens and the flavors meld together.
Finish with cream and herbs: Reduce the heat to low and stir in the heavy cream, mixing until the sauce turns a rich, velvety orange color. Add fresh basil if desired, and season with salt and black pepper to taste. Simmer for another 1–2 minutes to bring everything together.
Combine pasta and sauce: Add the drained rigatoni directly into the skillet with the sauce, tossing gently until every piece of pasta is coated. If the sauce seems too thick, add a splash of the reserved pasta water to loosen it.
Serve and garnish: Divide the pasta among bowls, sprinkle generously with freshly grated Parmesan cheese, and garnish with additional basil if desired. Serve immediately while hot and enjoy a restaurant-worthy meal at home.
