Preheat the oven to 450°F. Line two baking sheets with parchment paper and set a plate or tray nearby lined with paper towels for draining the zucchini after roasting.

Trim the ends off the zucchini, then use a mandoline to slice into ¼-inch thick “lasagna noodles.” Arrange the strips in a single layer on the prepared baking sheets. Drizzle with olive oil, sprinkle with 1 teaspoon of salt, and roast for 10 minutes. Once done, transfer the zucchini to the paper towel-lined plate, blot with another towel to remove excess moisture, and set aside to cool. Reduce the oven temperature to 375°F.

While the zucchini cools, cook the ground turkey, mushrooms, and onion in a large skillet over medium-high heat for 6–8 minutes, or until fully cooked. Stir in Italian seasoning, ½ teaspoon salt, ¼ teaspoon black pepper, and pasta sauce. Bring to a boil, then reduce heat and simmer uncovered for 5 minutes.

In a medium bowl, combine the ricotta cheese, egg, remaining salt and pepper, 1 cup mozzarella, and ¼ cup Parmesan. Mix well.

Lightly coat a 13×9-inch baking dish with cooking spray. Spread ½ cup of the meat sauce in the bottom of the dish. Layer with zucchini noodles, then spread half the ricotta mixture over the zucchini, followed by ⅓ of the meat sauce. Repeat the layers—zucchini, remaining ricotta, ⅓ more sauce. Finish with a final layer of zucchini, the remaining sauce, and top with the remaining mozzarella and Parmesan.

Bake uncovered for 40 minutes, or until the top is golden and bubbling. Let rest for 10–15 minutes before slicing and serving.