1. Preheat oven to 350.
2. Peel, slice and quarter tomatoes. Spread in a single layer on a double layer of paper towels to drain for at least 15 minutes. Sprinkle with salt to taste.
3. If desired, saute chopped onion for milder onion flavor.
4. Chop basil.
5. Mix together grated cheeses, eggs, chopped onions and half the chopped basil leaves to make topping. Salt and pepper to taste.
6. Gently squeeze out tomato pieces to drain off more liquid. Arrange the tomato pieces in an 8 square baking dish. There should be a generous layer of tomato.
7. Salt and pepper to taste. Sprinkle with the other half of the chopped basil and toss together gently.
8. Spoon topping over tomatoes, spreading to cover evenly.
9. Bake at 350 until tomatoes are tender, about 30 minutes.