1. Peel and slice the eggplant
2. Drop in a saucepan of boiling salted water and boil till tender.
3. Drain well
4. Butter a casserole dish.
5. Preheat the oven to 350°F
6. Layer ½ the eggplant in the baking dish and sprinkle a little cheese.
7. Pour 1/3 the sauce to cover the eggplant.
8. Top with the onion and tomatoes and cover with sauce.
9. Layer remaining eggplant slices and top with sauce and cheese.
10. Sprinkle the buttered crumbs on top
11. Bake in the preheated oven for 30 minutes until crust is golden brown.