1. Bring a large pot of salted water to a boil. Cook the rigatoni according to package instructions until al dente. Reserve 1 cup of pasta water, drain, and set pasta aside.

2. Heat olive oil in a large skillet over medium heat. Add diced onion and cook for 3–4 minutes until softened. Stir in the garlic and cook for 1 more minute until fragrant.

3. Add ground beef to the skillet, breaking it apart with a spatula. Cook until browned and fully cooked through, about 6–8 minutes. Drain any excess grease.

4. Stir in the tomato paste, Italian seasoning, red pepper flakes (if using), salt, and pepper. Cook for 2–3 minutes to enhance the flavor.

5. Pour in the beef broth and heavy cream. Stir to combine and simmer for 5–7 minutes to allow the sauce to thicken slightly.

6. Gradually stir in the Parmesan cheese until melted and incorporated. Add the mozzarella and stir until smooth and creamy.

7. Add the cooked rigatoni to the skillet and toss to coat with the sauce. Add reserved pasta water as needed for desired consistency.

8. Serve hot, garnished with fresh parsley or basil and additional Parmesan on the side.