Heat oven to 350°F. Mist a 9” x 13” casserole dish with olive oil cooking spray; alternatively rub with additional softened butter.

Melt 2 tbsp butter. Add the melted butter to the breadcrumbs and mix until the breadcrumbs are evenly moistened. Set aside.

Heat the remaining 4 tbsp butter in a 12” skillet over medium high heat until the butter melts then foams. Add the onion, toss to coat in the fat, and saute, stirring occasionally, until the onion softens, 6-7 minutes. Add the garlic and saute, stirring continuously, until fragrant, about 1 minute.

Add the zucchini and squash to the pan. Saute, stirring occasionally, until the zucchini and squash release their liquids, the liquid cooks off, and the vegetables are tender, about 15 minutes.

Add the diced tomatoes (including the canning liquid), basil, thyme, salt, and pepper. Stir to combine, then bring the liquid to a simmer; adjust the heat to maintain a steady simmer and cook for 5 minutes.

Scrape the mixture into the prepared casserole dish. Sprinkle the shredded cheese over the vegetable mixture, then sprinkle the breadcrumbs evenly over the casserole.

Transfer to the oven and bake for 30 minutes, until the cheese is melted, the topping is golden brown, and the casserole is bubbling. Rest five minutes, then garnish with fresh basil and serve hot or warm.