Vegetable Tian

from Barefoot in Paris, Ina Garten
also found here

Serves 4 to 6 (I will make a larger one next time)

3 Tablespoons olive oil
2 large yellow onions, cut in half and sliced
2 cloves garlic, minced
1 pound Yukon gold potatoes, unpeeled (2 potatoes)
3/4 pound zucchini (1 zucchini)
1 yellow squash
1 1/4 pounds medium tomatoes (plum/roma tomatoes)
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
1 tablespoon fresh thyme leaves, plus extra sprigs (I used dried crushed)
2 ounces Gruyere cheese, grated (I used Parmesan)
3 tablespoons Panko crumbs (optional)

Preheat the oven to 375 degrees F.

Brush a 9x13x 2-inch baking dish with 1 Tablespoon olive oil. In a medium saute pan, heat 1 Tablespoon 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, squash 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 with cheese* on top, and bake for another 30 minutes, or until browned. Serve warm.

*I wait unitl it is done and out of the oven to add the cheese

Can be made ahead of time, refrigerated and reheated at serving time.