Vegetable Tian

One of my favorite dishes of summer -- zucchini, tomatoes and potatoes with onion, garlic, a hint of thyme and a sprinkle of cheese. From Ina Garten:

• Good olive oil
• 2 large yellow onions, cut in half and sliced
• 2 garlic cloves, minced
• 1 pound medium round potatoes, unpeeled
• 3/4 pound zucchini
• 1-1/4 pounds medium tomatoes
• 1 teaspoon kosher salt
• 1/2 teaspoon freshly ground black pepper
• 1 tablespoon fresh thyme leaves, plus extra sprigs
• 2 ounces Gruyère cheese, grated

Preheat the oven to 375 ­degrees.

Brush a 9 x 13 x 2­-­inch baking dish with olive oil. In a medium sauté pan, heat 2 tablespoons of olive oil and cook the onions over medium­-­low heat for 8 to 10 minutes, until translucent. Add the garlic and cook for another minute. Spread the onion mixture on the bottom of the baking ­dish.

Slice the potatoes, zucchini, and tomatoes in 1/4-inch-thick slices. Layer them alternately in the dish on top of the onions, fitting them tightly, making only one layer. Sprinkle with salt, pepper, thyme leaves, and thyme sprigs and drizzle with 1 more tablespoon of olive oil. Cover the dish with aluminum foil and bake for 35 to 40 minutes, until the potatoes are tender. Uncover the dish, remove the thyme sprigs, sprinkle the cheese on top, and bake for another 30 minutes, or until browned. Serve ­warm.