4to 5 medium summer squash, zucchini and yellow squash, sliced thin
1/2medium yellow onion, diced
1 1/2cupsshredded mozzarella
2teaspoons kosher salt, plus more to taste
4tablespoonsextra-virgin olive oil, divided
fresh pecorino-Romano or Parmigiano-Reggiano cheese, to serve
Preheat the oven to 375°F.
On medium heat, toast the breadcrumbs in a pan with 2 tablespoons of olive oil and a pinch of salt until golden-brown, stirring often. Set aside.
Trim the ends of the squash and slice thin, about 1/8" to 1/4" thick.
Toss the sliced zucchini with 2 teaspoons of kosher salt and let season and drain in a colander for five to 10 minutes.
Coat the bottom of a casserole pan or baking dish with 2 tablespoons of olive oil. Ladle one cup of marinara into baking dish and spread over the bottom. Scatter the diced onions over the marinara.
Without rinsing the summer squash, shingle in a circular pattern around the casserole. Bake, loosely tented with foil, for about 30 minutes, until fork tender.
Remove the foil. Top the zucchini and yellow squash with another cup of marinara. Top with the shredded mozzarella, then the breadcrumbs, a generous pinch of salt, and bake -- uncovered -- for an additional 30 minutes, until the squash is soft and everything is melted and bubbling. Let cool for 5 to 10 minutes before serving.