Brown the sausage: In a large pot or Dutch oven over medium-high heat, cook the sausage, breaking it up as it browns, about 8-10 minutes, until no longer pink and it reaches 160°F. Drain off excess grease, leaving a bit behind for flavor.
Sauté the aromatics: Add the onion to the pot and cook for 3-4 minutes until softened. Stir in the garlic and cook 1 minute more.
Build the tomato base: Stir in the crushed tomatoes, tomato paste, Italian seasoning, and red pepper flakes if using. Bring to a simmer and cook for 3-4 minutes, until slightly reduced.
Add the broth and cook the rigatoni: Pour in the chicken broth and stir in the rigatoni. Cover and simmer for 18-20 minutes, stirring occasionally, until the pasta is tender.
Finish creamy: Reduce the heat to low and stir in the heavy cream and parmesan. Simmer for 2-3 minutes until glossy and slightly thickened.
Serve: Top with fresh basil and extra parmesan.
Notes
Let the tomatoes reduce for a few minutes before adding the broth and cream, it builds real depth into the sauce. Cook sausage to an internal temperature of 160°F.