Preheat oven to 375°F (190°C). Cook the ziti until just al dente; drain.
Brown the sausage with the onion in a large skillet, breaking it up. Add the garlic and cook 1 minute.
Stir in the marinara sauce, crushed tomatoes, and Italian seasoning. Simmer 10 minutes.
In a bowl, mix the ricotta, egg, 1 cup of the mozzarella, and the Parmesan.
Toss the pasta with the sausage sauce and the ricotta mixture. Spread in a 9x13 baking dish.
Top with the remaining 1 cup mozzarella. Bake 25 minutes until bubbly and golden.
Let rest 10 minutes, then garnish with fresh basil.