In a cast iron pan on medium high, heat the oil, garlic, and onion, for 3 to 5 minutes. Add the tomatoes; stir occasionally till thickened, 5 to 10 minutes.
In a large bowl, mix the ricotta, zest, and herbs; season with salt and pepper.
Heat the oven to 400°F. Spoon out half the sauce; set aside. Now do layers in the pan: half the vegetables; half the ricotta; repeat; the rest of the sauce; mozzarella. Bake in the oven, lid on, till tender, 20 to 30 minutes. Uncover and bake till the cheese is bubbly; 5 to 10 minutes. Using oven mitts, remove the pan. Cool. Slice. Feeds 6.
