Wash and peel the eggplants and zucchini and cut into slices. Blanch them briefly, drain, and set aside. Peel the tomatoes; cut the tomatoes and peppers in to slices. Mince the onions and brown lightly in a frying pan with two spoonfuls of olive oil. In a tian (earthenware dish), first put the onions with their oil to form the first layer. Sprinkle on a handful of grated Parmesan, then put in the zucchini. Sprinkle another handful of parmesan pour a little oil over the whole layer, then put in the eggplants. Arrange the pepper slices between the eggplant slices and sprinkle on the rest if the Parmesan. Bake (1 hr) at 200°C.