Arrange tomatoes, zucchini, onion, and eggplant in a spiral, alternating them, in the casserole dish. If needed, cut the eggplant slices into quarters to match the size of the other veggies.
5 Drizzle with olive oil on top and sprinkle salt and pepper.
6 Bake for 40 minutes or until sauce is bubbly at the edges.