I served this recently at a family dinner and it was a HUGE hit! I served it with lasagna but it would go well with just about anything and it super easy to put together. I love that it can be done ahead of time!
Topping:
1/4 cup breadcrumbs
1/3-1/2 cup grated Parmesan cheese
1 tablespoon olive oil
2 teaspoons finely chopped parsley
1 teaspoon garlic powder
1 teaspoon onion powder
2 teaspoons finely chopped thyme
Gratin:
Try to find the three items below similar in size:
- 2 medium zucchini squash
- 2 medium yellow zucchini
- 3 to 4 plum or Roma tomatoes
1/4 cup olive oil, divided
1 1/4 teaspoons salt, divided
1/4 teaspoon freshly ground black pepper
1 small onion, thinly sliced or diced
1/2 medium bell pepper, halved and thinly sliced (I used orange bell pepper)
3 cloves garlic, minced
Directions:
Arrange a rack in the middle of the oven and heat to 375°F. Lightly coat an 8x8-inch baking dish with oil; set aside.
Make the topping:
Place all the ingredients in a small bowl and mix until combined and set aside.
Make the gratin:
- Cut the zucchini, 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 the pepper. Toss to combine and set aside.
- Heat the remaining 2 tablespoons oil in a large frying pan over medium heat. Add the onions, bell pepper, and remaining 1/4 teaspoon of salt. Cook, stirring occasionally, until the onions are tender and lightly browned, 10 to 12 minutes. Stir in the garlic and cook about 1 minute more.
- Transfer the onion mixture to the baking dish and spread into an even layer. Place the 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.
- Bake for 30 minutes. Uncover and bake until the vegetables are tender and the edges and topping are browned, 15 to 20 minutes more.
Make ahead: I made my advance and refrigerated it, but didn't add the topping on until I was ready to bake it.