01 -
Preheat the oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish.
02 -
Cook the ziti pasta according to package instructions, drain, and set aside.
03 -
In a large skillet, heat the olive oil over medium heat. Add the onion and garlic, sautéing until fragrant, about 3 minutes. Add the chopped spinach, cooking until wilted. Stir in the marinara sauce, basil, oregano, red pepper flakes (if using), salt, and black pepper. Simmer for 5 minutes.
04 -
In a mixing bowl, combine ricotta cheese, ½ cup mozzarella, Parmesan, egg, and heavy cream (if using), mixing until smooth.
05 -
Combine the cooked ziti with the spinach marinara sauce in a large bowl. Spread half of the pasta mixture into the prepared baking dish. Dollop ricotta mixture over the pasta, then top with the remaining pasta. Sprinkle the remaining mozzarella cheese on top.
06 -
Cover with foil and bake for 20 minutes. Remove the foil and bake for another 10-15 minutes until cheese is melted and bubbly. Let the dish cool for a few minutes before serving.