Preheat oven to 425°.
Slice tomatoes into 8 - 10 slices. Place on a paper towel to drain excess water.
Slice eggplant into 8 - 10 slices, about 1¼ to ½ thick. Sprinkle slices of eggplant with salt to withdraw some of the moisture from them. Let the eggplant sit for about 20 minutes in a colander, then dry the pieces with a tea towel or paper towel to remove as much moisture as possible.
Slice the onion into rings.
Coat all the vegetables with a light layer of olive oil and season with salt and pepper.
Grease or spray a 9 X 11 baking pan or casserole dish. Layer the vegetables, starting with the eggplant then followed by the onion and tomato. Sprinkle with dried basil. Bake at 425° for 30 minutes, covered.
Add mozzarella medallions and bake another 10 minutes, uncovered.
Once the mozzarella has melted, removed the eggplant tomato mozzarella bake from the oven and allow to cool about 5 to 10 minutes. Top with a sprinkling of chopped fresh basil and serve warm.