Baked Mediterranean Vegetable Tian

Preheat oven to 375°F / 190°C. Heat 1 tablespoon of olive oil in a skillet over medium heat. Sauté diced onions and garlic until soft and translucent (5 minutes). Stir in crushed tomatoes, Italian seasoning, salt, and pepper. Simmer for 5 minutes, then spread evenly over the bottom of your baking dish.

Using a mandoline or sharp knife, slice the zucchini, yellow squash, eggplant, and Roma tomatoes into uniform rounds approximately ⅛-inch / 3mm thick.

Arrange the sliced vegetables vertically in the baking dish over the tomato sauce, alternating between zucchini, eggplant, yellow squash, and tomato rounds. Pack them tightly in snug rows until the dish is filled.

Drizzle the arranged vegetables with the remaining 2 tablespoons of olive oil. Season generously with salt, black pepper, and fresh thyme leaves. Cover tightly with foil or parchment paper.

Bake covered at 375°F / 190°C for 40 minutes to steam the vegetables until tender.

Remove the cover (and sprinkle with grated Parmesan if desired). Return to the oven and bake uncovered for an additional 15 to 20 minutes until the edges are golden brown and caramelized. Serve warm.