Cook pasta by bringing a large pot of salted water to a boil, add rigatoni and cook until al dente, about 10-12 minutes. Reserve 1/2 cup of pasta water, then drain.

In a large skillet, heat olive oil and brown ground beef for 5-7 minutes until no longer pink. Drain excess fat.

Add chopped onion to skillet and sauté for 3-4 minutes. Stir in minced garlic and cook for 1 more minute.

Add Italian seasoning and red pepper flakes, then pour in beef broth and simmer for 2-3 minutes.

Stir in heavy cream and cook for 2-3 minutes, avoiding boiling to prevent curdling.

Mix in grated Parmesan and shredded mozzarella, adjusting seasoning with salt and pepper.

Combine drained rigatoni with the sauce, adjusting consistency with reserved pasta water as needed.

Serve hot, garnished with chopped parsley.