Peel and slice the eggplant in 3/4 inch slices. Place eggplant in about 2 inches of salted water in large saucepan. Cover and boil until soft, about 15 minutes.

Drain in colander and press out excessive water. Let cool a bit. Mash eggplant and place in large mixing bowl.

Grate the cheese and add the Parmesan cheese and mix together.

In saucepan, melt butter and add onion and cook until tender, but not browned.

To the eggplant, add the breadcrumbs, butter and onions, oregano, 3 eggs, beaten, some pepper and 1 teaspoon of salt. Add just less the one half of the cheese mixture and mix to combine.

Butter or spray a shallow 2 quart casserole and place 1/2 of the sliced tomatoes on the bottom. Now place the eggplant mixture on top. Now place the remaining sliced tomatoes on top. Spread the grated cheese mixture on top of the tomatoes.

Bake for 45 minutes in a 375 degree oven.