We take the leftover ziti out of the fridge, it is already in an 8-inch square glass baking dish and it was tossed with a little sauce last night to prevent it from sticking together. We stir in about 1 1/2 cups of sauce and most of the ricotta. We spread the remaining ricotta, Locatelli, and mozzarella on top of the ziti. We cover the baking dish with aluminum foil and bake for 20 minutes.
After 20 minutes, the sauce is bubbling. We uncover and continue baking for another 25 minutes. We want the top to get crispy and slightly browned. We take the dish out of the oven and let it sit for a few minutes before serving while we heat the remaining sauce in the microwave.