Cut the ends of the eggplants, then cut in slices of 1/2 inch thickness. In an oven proof dish, mix eggplants, garlic and half oil, half salt and half pepper (I mixed everything in a large bowl). Lay out the eggplant slices in one layer in a baking dish (I used a large baking pan and I made half recipe). Cook under the preheated grill of the oven (6 inches apart from the grill), for about 6 minutes or until golden (flip them one time).
In a large baking dish (I sprayed it with PAM), put half of the eggplants, cover with onion slices and sprinkle with half of the italian seasoning. Drizzle with half of the remaining oil and sprinkle with half of the remaining salt and pepper. Do another layer the same way with tomato slices then cover with remaining eggplant. Add italian seasoning. Cook in the preheated oven of 400F for about 20 minutes or until bubbly and golden. Sprinkle with asiago and mozzarella and put under preheated grill for 1 minute or until the cheese has melted and is golden.