Preheat the oven to 375°F. Lightly grease a 9x13 inch baking dish.
Bring a large pot of salted water to a boil. Cook the ziti 1 minute less than package directions. Drain.
Heat olive oil in a skillet over medium heat. Sauté the onion 4 to 5 minutes, then add garlic and cook 1 minute more.
Stir in the marinara, Italian seasoning, salt, and pepper. Simmer 5 minutes.
In a bowl, mix the ricotta, beaten egg, and half the Parmesan.
Toss the drained ziti with the sauce. Spread half in the baking dish.
Dollop the ricotta mixture over the pasta. Top with remaining ziti.
Sprinkle with mozzarella and remaining Parmesan.
Cover with foil and bake 20 minutes. Uncover and bake 10 minutes more, until bubbly and golden.
Let rest 10 minutes, then top with fresh basil and serve.