Preheat oven to 375°F and grease a 9x13-inch baking dish with 1 tablespoon of olive oil, coating the bottom and sides. Set aside while you prepare vegetables.
¼ cup olive oil
Slice eggplant, zucchini, and tomatoes into ⅛-inch rounds using a mandoline or a sharp knife. Pat tomato slices dry with paper towels to remove excess moisture. Slice onion into thin half-moons and mince garlic.
1 medium eggplant, 2 medium zucchini, 4 medium tomatoes, 1 large onion, 4 cloves garlic
Spread the onion slices and minced garlic evenly across the bottom of the prepared baking dish to create an aromatic base layer. Drizzle with 1 tablespoon olive oil and sprinkle with a pinch of salt.
1 large onion, 4 cloves garlic, ¼ cup olive oil, 1 tsp salt
Layer the vegetable slices vertically in an alternating pattern of eggplant, zucchini, and tomato, standing them upright and leaning slightly. Leave small gaps between slices to allow steam to escape. Drizzle the remaining olive oil over the vegetables, then sprinkle evenly with herbs de Provence, salt, and black pepper.
1 medium eggplant, 2 medium zucchini, 4 medium tomatoes, ¼ cup olive oil, 2 tsp herbs de Provence, 1 tsp salt, ½ tsp black pepper
Roast uncovered in the preheated oven for 40 to 45 minutes until vegetables are tender when pierced with a fork and edges turn golden brown. If using cheese, sprinkle it over the top during the last 10 minutes of roasting. Remove from oven and let rest for 10 minutes before serving.
¼ cup Parmesan or Gruyère cheese
