Preheat the oven to 375 degrees F and lightly grease a 9x13 inch baking dish.
Bring a large pot of salted water to a boil and cook the ziti until just al dente. Drain and set aside.
In a mixing bowl, stir together the ricotta, egg, Italian seasoning, a pinch of salt, and a few grinds of black pepper until smooth.
Spread 1 cup of marinara sauce across the bottom of the prepared baking dish.
Add half the cooked ziti in an even layer, then spoon the ricotta mixture over the pasta and spread it gently.
Pour 1 cup of marinara over the ricotta layer and sprinkle with 1 cup of mozzarella.
Add the remaining ziti, the last cup of marinara, the rest of the mozzarella, and all of the Parmesan.
Cover with foil and bake for 20 minutes, then uncover and bake 10 minutes more until the cheese is bubbly and lightly browned.