Eggplant zucchini squash tomatoes bell peppers mandoline ¼-inch thin rounds. Salt eggplant slices colander 15 minutes sweat rinse pat dry paper towels. Stack separate piles even.
10-inch skillet medium heat 2 tbsp olive oil. Add 1 sliced onion 2 minced garlic sauté 5 minutes soft. Pour 15 oz crushed tomatoes 2 tsp thyme 1 tsp herbes de Provence simmer 10 minutes thick fragrant.
9-inch round baking dish pour sauce even base. Parchment circle trace cut line dish. Arrange veggie slices upright alternating eggplant zucchini squash tomato pepper spiral tight pretty. Drizzle 1 tbsp olive oil sprinkle 1 tsp salt ½ tsp pepper thyme sprigs.
Preheat 375°F. Foil tent loose baking dish 30 minutes steam tender. Foil off bake 10 minutes veggies caramel edges sauce bubble. Rest 10 minutes slices hold.