Slice eggplant 1/2 inch thick. Pare off skin and dice to make about 5 cups of diced eggplant. Saute eggplant in 3 tablespoons butter for 5 minutes. Place in buttered casserole with alternate layers of onions, tomatoes, and 3/4 cup grated cheese. Season each layer with salt and pepper. Top with crumbs mixed with remaining cheese an ddot with butter. Bake until vegetables are tender and top is browned, about 35 minutes.