Summer Vegetable Bake

1/4 cup fresh breadcrumbs
1/3 cup freshly grated Asiago cheese
1 tablespoon olive oil
2 teaspoons finely chopped flat leaf parsley
2 teaspoons finely chopped fresh thyme

Gratin:

2 medium zucchini, cut into 1 1/2 inch rounds
2 medium yellow squash, cut into 1 1/2 inch rounds
4 plum or Roma tomatoes, cut into 1 1/2 inch rounds
1/4 cup olive oil, divided
1 1/4 teaspoons sea salt, divided
1/4 teaspoon freshly ground black pepper
1 small sweet onion, thinly sliced
1/2 medium orange or red bell pepper, halved and thinly sliced
3 cloves garlic, minced

1. Heat oven to 375°F. Lightly coat an 8×8-inch baking dish with oil.
2. Place all topping ingredients in a small bowl and mix until combined; set aside.
3. Slice the zucchini, yellow squash, and tomatoes crosswise into 1/4-inch rounds, place in a large bowl, add 2 tablespoons of the oil, 1 teaspoon of the salt, and 1 teaspoon pepper. Toss to combine; set aside.
4. Heat a large frying pan over medium heat. Add 2 tablespoons oil. When oil shimmers, add onions, bell pepper, and remaining 1/4 teaspoon of salt. Cook, stirring occasionally, until the onions are tender and lightly browned, about 11 minutes. Stir in garlic and cook until fragrant, about 1 minute more.
5. Transfer the onion mixture to the baking dish and spread in an even layer. Place zucchini, squash, and tomato slices on the onions, arranging them on their sides and alternating the slices as you go. Sprinkle the breadcrumb mixture over the top. Cover tightly with aluminum foil.
6. Bake for 30 minutes. Uncover and bake until the vegetables are tender and the edges and topping are browned, about 20 minutes more.