Eggplant Napoli

In a skillet, saute chopped onions in oil. Add tomato puree, water, salt, oregano and pepper. Bring to a boil and simmer for 15 minutes. In a greased baking dish, alternate thin layers of sliced eggplant, tomato sauce and half of the grated cheese, starting with a layer of eggplant and ending with a layer of tomato sauce. Bake in moderate oven (350 F) for 1 hour. Minutes before removing from oven, sprinkle remaining grated cheese over top and continue heating until cheese melts.