Summer Vegetable Gratin

Steps were taken in order to eliminate excess moisture from the vegetables. Salting the zucchini and summer squash, placing the tomatoes on top, and baking the casserole uncovered allowed the tomatoes to roast and caramelize. 

• 6 Tbls extra virgin olive oil
• 1 pound zucchini, ends trimmed and sliced into 1/4-inch slices
• 1 pound yellow summer squash, ends trimmed and sliced crosswise into 1/4-inch slices
• 2 tsp table salt
• 1 1/2 pounds ripe tomatoes (3 to 4 large) sliced 1/4-inch thick
• 2 med. onions, halved lengthwise and sliced-thin pole-to-pole (about 3 cups)
• 3/4 tsp ground black pepper
• 2 medium garlic cloves, minced or pressed through a garlic press (about 2 tsp)
• 1 Tbsp minced fresh thyme leaves
• 1 large slice white sandwich bread torn into quarters
• 2 ounces grated Parmesan cheese (about 1 cup)
• 2 medium shallots, minced (about 1/4 cup)
• 1/4 cup chopped basil leaves

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1. Adust oven rack to upper-middle position and heat oven to 400 degrees. Brush 13- by 9-inch baking dish with 1 Tbsp. olive oil; set aside
2. Toss zucchini and summer squash slices with 1 tsp salt in a large bowl; transfer to colander set over bowl. Let stand until zucchini and squash release at least 3 Tbsp of liquid, about 45-minutes. Arrange slices on a triple-layer paper towels; cover with another triple-layer paper towels. Firmly press each slice to remove as much liquid as possible.
3. Place tomato slices in a single layer on double-layer paper towels and sprinkle evenly with 1/2 tsp salt; let stand 30 minutes. Place second double layer paper towels on top of tomatoes and press firmly to dry tomatoes.
4. Meanwhile, heat 1 Tbls. oil in 12-inch nonstick skillet over medium heat until shimmering. Add onions, remaining 1/2 tsp. salt, and 1/4 tsp pepper; cook, stirring occasionally, until onions are softened and dark golden brown, 20 to 25 minutes, set onions aside.
5. Combine garlic, 3 Tbsp. oil, remaining 1/2 tsp. pepper, and thyme in small bowl. In large bowl, toss zucchini and summer squash in half of oil mixture, then arrange in greased baking dish. Arrange carmelized onions in even layer over squash. Slightly overlap omato slices in single layer on top of onions. Spoon remaining garlic-oil mixture evenly over tomatoes. Bake until vegitables are tender and tomatoes are starting to brown on edges, 40 to 45 minutes.
6. Meanwhile, process bread in food processor until finely ground, about 10 seconds. (You should have about 1 cup crumbs.) Combine bread crumbs, remaining 1 Tbsp. oil, Parmesan, and shallots in medium bowl. Remove baking dish from oven and increase heat to 450 degress.. Sprinkle bread-crumb mixture evenly on top of tomatoes. Bake gratin until bubbling and cheese is lightly browned, 5 to 10 minutes. Sprinkle with basil and let sit at room temperature 10 minutes before serving.

Taken from Cooks Illustrated issue 93, July and August 2008. Page 10-11.