Preheat and prep: Heat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with butter or nonstick spray.

Cook the pasta: Bring a large pot of salted water to a boil. Add ziti and cook until just shy of al dente (about 1–2 minutes less than package time). Drain and set aside.

Build the sauce: In a large skillet, warm olive oil over medium heat. Add onion and cook until soft and translucent, about 5 minutes. Stir in garlic for 30 seconds until fragrant.

Add tomatoes and seasoning: Pour in crushed tomatoes and tomato paste. Stir in Italian seasoning, red pepper flakes if using, and season with salt and pepper. Simmer 8–10 minutes to thicken slightly. Taste and adjust seasoning.

Mix the ricotta layer: In a bowl, combine ricotta, 1 cup mozzarella, 1/2 cup Parmesan, the egg, a pinch of salt, and a few grinds of pepper. Stir until smooth.

Combine pasta and sauce: Add the drained pasta to the skillet with the sauce and toss until every piece is coated.

Assemble: Spread half the sauced pasta in the baking dish. Dollop half the ricotta mixture over it in spoonfuls. Repeat with the remaining pasta and ricotta. Sprinkle the top with the remaining mozzarella and 1/4 cup Parmesan.

Bake: Cover loosely with foil (tent it so it doesn’t stick to the cheese) and bake 20 minutes. Remove the foil and bake another 10–15 minutes, until the cheese is melted and golden at the edges.

Rest and serve: Let it rest 5–10 minutes so it sets slightly. Top with chopped basil or parsley. Serve warm.