Cook the beef: In a large skillet, brown the ground beef over medium heat. Drain any excess fat, then stir in the marinara sauce and Italian seasoning. Set aside.

Boil the pasta: Cook the rigatoni in salted boiling water until al dente. Drain well.

Mix the ricotta layer: In a bowl, combine ricotta, Parmesan, egg, garlic salt, and a pinch of salt and pepper. Toss this mixture with the cooked pasta until coated.

Assemble: In a greased casserole dish, spread half of the pasta mixture, then top with half the beef sauce and half of the mozzarella and Gruyère. Repeat layers and finish with plenty of cheese on top.

Bake: Bake uncovered at 375°F for 25–30 minutes, until bubbly and golden brown on top.