Preheat Oven to 400°F

Spread 1/2 cup marinara over the bottom of a deep pie dish or rectangular casserole dish.

Thinly slice onion and sprinkle over marinara

Thinly slice eggplant, zucchini, yellow squash, and tomatoes (about 1/4" thick) slice pieces in halfs or quarters to make similar in size. Layer in casserole dish like dominoes.

Sprinkle salt, pepper, oregano, and basil over vegetables. Then pour remaining 1/2 cup marinara over everything.

Cover with tin foil and cook for 30 minutes

Remove tin foil, sprinkle mozzarella and return to oven for 10-15 minutes until cheese is melted and golden brown.