Get ready. Position one rack in the middle and one rack in the top third of your oven. Preheat to 200°C (400°F). Brush a large sheet pan and a 9 x13-inch baking dish with a little olive oil.

Roast the zucchini. Arrange the zucchini in the sheet pan in one layer (they can touch but should not overlap). Season the top of the zucchini slabs with kosher salt and black pepper, then brush with olive oil.

Bake. Place on the middle rack until the zucchini are soft and somewhat pliable (they do not need to be fully cooked through), about 15 minutes. Remove from the oven but keep the oven on. Carefully and lightly pat the zucchini with a paper towel to remove excess moisture.

Assemble the zucchini parmesan casserole. Spread about ½ cup of the sauce on the bottom of the prepared baking dish. Lay a few zucchini slabs in one single layer to cover the sauce. Top with about a third of the mozzarella and ¼ cup of the grated parmesan. Repeat two more times in the same pattern, ending with the last of the zucchini on top.

Bake then broil. Place the baking dish on the center rack of the heated oven and bake until the zucchini is tender and the cheese has fully melted, about 20 minutes. For a little more color, transfer the baking dish to the top rack. Turn your oven to broil and keep an eye on things. Remove from the oven when the top layer is golden brown, about 2 minutes.

Rest. Remove the zucchini parmesan from the oven and allow the casserole to rest for about 10 to 15 minutes.

Serve: When the cheese and liquids have settled, cut the zucchini parmesan into 12 squares. Garnish with the torn basil and serve.