Cook the meat:
In a large skillet, sauté onion and garlic in a little olive oil until softened.
Add ground beef and Italian sausage, breaking it up as it cooks. Cook until browned.
Build the sauce:
Stir in marinara, Italian seasoning, red pepper flakes (if using), salt, and pepper.
Let simmer for 5–10 minutes.
Make it creamy:
Stir in heavy cream and let the sauce simmer until rich and smooth.
Cook the pasta:
Boil rigatoni in salted water until just under al dente. Drain.
Mix & layer:
Combine pasta with the sauce. Stir in about 1 cup mozzarella and a sprinkle of Parmesan.
Bake:
Transfer to a baking dish. Top with remaining mozzarella and Parmesan.
Bake to perfection:
Bake at 375°F for 20–25 minutes, then broil 2–3 minutes until golden and bubbly.