Cook the Rigatoni:
Bring a large pot of salted water to a boil.
Cook rigatoni until just shy of al dente (it will finish cooking in the sauce).
Reserve 1 cup of pasta water, then drain and set aside.
Cook the Italian Sausage:
Heat olive oil in a large skillet over medium heat.
Remove sausage from casing and break into crumbles.
Cook until browned, about 5-7 minutes. Remove and set aside.
Sauté the Aromatics:
In the same skillet, add onions and cook until softened.
Stir in garlic and cook for 30 seconds.
Add tomato paste and stir until it deepens in color.
Simmer the Tomato Sauce:
Pour in crushed tomatoes, oregano, basil, red chili flakes, salt, and pepper.
Bring to a simmer and cook for 15 minutes, stirring occasionally.
Make it Creamy:
Lower the heat and stir in heavy cream.
Add back the cooked sausage.
Stir in butter and parmesan cheese, mixing well.
Toss the Pasta in the Sauce:
Add cooked rigatoni into the sauce.
Stir well, adding reserved pasta water if needed to loosen the sauce.
Serve & Garnish:
Plate the pasta and top with extra parmesan cheese and fresh basil.
Serve immediately and enjoy!