Preheat your oven to 350°F (177°C) to ensure even cooking.

Cook the rigatoni in salted boiling water until al dente, about 8-10 minutes. Drain and reserve.

Sauté diced onion in olive oil for 3-4 minutes until softened, then add garlic and sauté for another minute.

Brown the ground beef in the skillet for 5-7 minutes; ensure it is cooked evenly.

Pour in the marinara sauce and simmer for 5 minutes; adjust seasoning with salt and pepper.

Fold the cooked rigatoni into the meat sauce mixture until well-coated.

Transfer the rigatoni mixture to a 13x9 inch baking dish and spread evenly.

Cover loosely with aluminum foil and bake for 20 minutes.

Remove foil, sprinkle mozzarella cheese on top, and bake uncovered for an additional 10 minutes.

Let the rigatoni rest for a few minutes before serving, garnished with fresh basil.