Preheat oven to 350. Place eggplant in a large bowl. Sprinkle with salt. Add vinegar and cover with water. Let stand 10 minutes. Remove and pat dry. While eggplant is soaking, combine tomatoes, garlic and onion in a non-reactive saucepan and simmer 5 minutes. Arrange eggplant in oiled baking dish. Cover with tomatoes. Bake 20 minutes. Sprinkle with cheese and bake another 10-15 minutes or until cheese is melted.