Peel aubergine, cut in thin slices, sprinkle with salt and let stand at room temperature in a bowl for 2 hours. Drain and wipe aubergine. Fry lightly in olive oil until soft and golden. Drain on paper towels. Saute the onions.
In pie crusts layer the aubergine, pepper, cheeses, cream and dots of butter. Repeat the layers with the onions and then the tomatoes. Bake at 375 for 45 to 60 minutes.