Brown the Italian sausage in a pan.
Add the diced onion and bell pepper and cook for 5 minutes until softened.
Season with salt, pepper, garlic powder, Italian seasoning, and crushed red pepper flakes.
Stir in the tomato paste and cook for 3-4 minutes.
Pour in the tomato sauce and beef stock.
Add the heavy cream and bring to a boil.
Add the rigatoni pasta, cover and simmer for 12 minutes until the pasta is cooked.
Remove from heat and let stand for a couple minutes to thicken.
Stir in grated Parmesan cheese (optional).
