Zucchini and Tomato Tian with Caramelized Onions—Tian de Courgettes aux Tomates
Hailing from Provence and named for the region's popular terra-cotta dishes, tian is a combination of summer vegetables perfumed with olive oil and thyme and crusted with Gruyère cheese. The trick to a great tian is figuring out how to ensure perfectly cooked vegetables; mushy or undercooked vegetables will not do. We lined the dish with a layer of caramelized onions, to which we added some minced garlic to achieve full aromatic flavor. Similar-size zucchini and summer squash plus plum tomatoes, which have a similar diameter to squash, made up the rest of the vegetables. Slicing them all on a mandoline gave us perfect slices in seconds. Alternating the vegetable slices and keeping them fairly tightly shingled gave us the look we wanted and kept the whole dish sliceable. As for cooking the tian, we found that covering the baking dish with foil trapped the heat and partially steamed the vegetables, allowing them to keep their moisture. After they'd steamed for 30 minutes, we sprinkled cheese over the top and returned the dish to the oven for the second phase of cooking.
Servings: 6
Ingredients
- ¼ cup extra-virgin olive oil divided
- 3 onions halved and sliced ¼ inch thick (about 3 cups)
- Salt and pepper
- 2 garlic cloves minced
- 1 pound zucchini trimmed and sliced 1/4 inch thick
- 1 pound yellow squash trimmed and sliced 1/4 inch thick
- 1 pound plum tomatoes cored and sliced 1/4 inch thick
- 1 teaspoon minced fresh thyme
- 2 ounces Gruyère cheese shredded (1/2 cup)
Instructions
BEFORE YOU BEGIN
- Try to buy squash and tomatoes that have roughly the same diameter. Slicing the vegetables ¼ inch thick is crucial for the success of this dish; use a mandoline or a food processor fitted with a slicing disk. You can also slice them carefully by hand using a very sharp knife. An oven-safe Provençal-style gratin dish can be substituted for the 13 by 9-inch baking dish, as long as it’s of similar size.
INSTRUCTIONS
- Adjust oven rack to middle position and heat oven to 375°F. Brush 13 by 9-inch baking dish with 1 tablespoon oil; set aside.
- Heat 2 tablespoons oil in 12-inch nonstick skillet over medium heat until shimmering. Add onions and ½ teaspoon salt and cook until softened and lightly browned, 12 to 15 minutes. Stir in garlic and cook until fragrant, about 30 seconds. Spread onion mixture on bottom of prepared dish.
- Alternately shingle zucchini, yellow squash, and tomatoes into single layer of 4 tightly fit rows on top of onions. Sprinkle with thyme, drizzle with remaining 1 tablespoon oil, and season with salt and pepper. Cover dish with aluminum foil and bake until vegetables are tender, about 30 minutes.
- Remove foil, sprinkle Gruyère over top, and continue to bake until bubbling around edge and lightly browned on top, 20 to 30 minutes longer. Let rest for 10 minutes before serving.