Turn your pasta into a hearty dump-and-serve casserole. Simply combine uncooked rigatoni, loose Italian sausage and ricotta in a baking dish, cover with marinara sauce and bake. For the final step, top it with a generous amount of mozzarella and pop it back in the oven until the cheese is melted and bubbly.
Preheat the oven to 425 degrees F. Generously grease the bottom and sides of a 9-by-13-inch casserole dish with the butter.
Stir together the marinara, beef broth, tomato paste, garlic, 1/2 teaspoon salt and 1/4 teaspoon pepper in a medium bowl.
Spread half the pasta in an even layer in the bottom of the prepared dish. Break the sausage into pieces and scatter half on the pasta. Dollop with half of the ricotta. Pour half of the marinara mixture over the top. Repeat with a second layer of pasta, sausage, ricotta and the marinara mixture.
Cover with aluminum foil and bake until the pasta is al dente, about 50 minutes.
Uncover and sprinkle the mozzarella on top. Bake uncovered until the mozzarella is melted and bubbly, about 10 minutes.