Brown the Italian sausage in a pan.
Add the diced onion and bell pepper and cook until softened.
Add the garlic and cook for another minute.
Stir in the tomato paste and cook for a few minutes.
Season with Italian seasoning, crushed red pepper flakes, salt, and pepper.
Add the tomato sauce, rigatoni, chicken stock, and heavy cream.
Bring to a simmer, then reduce heat and cover. Cook for 12-15 minutes until the pasta is done.
Remove from heat and let stand for a couple minutes.
Serve with freshly grated Parmesan cheese.
