Preheat oven to 375°F (190°C). Brown 1 lb sausage in a skillet with olive oil over medium-high heat until no pink remains, about 5 minutes. Add onion, cook 3-4 minutes, then garlic for 30 seconds.

Pour in 28 oz crushed tomatoes and 2 cups water. Stir in Italian seasoning, 1 tsp salt, and pepper. Simmer briefly, scraping up browned bits, then remove from heat.

Mix 15 oz ricotta, 1 cup mozzarella, ½ cup Parmesan, 1 egg, and a pinch of salt and pepper until smooth.

Layer: 1 cup sauce in a 13x9-inch dish. Half the uncooked ziti, then half remaining sauce. Dollop and spread all ricotta mixture. Add rest of ziti, last of sauce, and remaining 1 cup mozzarella. Press down gently, cover tightly with foil.

Bake covered 45 minutes. Uncover, bake until golden and bubbling, 15-20 minutes. Rest 10 minutes, then serve with extra Parmesan.