01 - Preheat the oven to 400°F. Lightly grease a large baking dish with cooking spray or a small amount of oil.
02 - Slice each zucchini in half lengthwise. Using a spoon, scoop out the flesh to create boats, leaving about 1/4-inch border. Chop the scooped flesh and set aside.
03 - Heat olive oil in a large skillet over medium heat. Add the diced onion and cook for 2–3 minutes until slightly softened and translucent.
04 - Add minced garlic and cook for 30 seconds until fragrant. Add ground turkey, breaking up with a spoon, and cook until browned and cooked through, about 5–6 minutes.
05 - Stir in the chopped zucchini flesh, spinach, cherry tomatoes, oregano, red pepper flakes, salt, and black pepper. Sauté until spinach is wilted and excess moisture evaporates, 2–3 minutes.
06 - Remove skillet from heat. Stir in basil pesto, half the mozzarella cheese, half the Parmesan cheese, parsley, and basil until well combined.
07 - Arrange zucchini boats in the prepared baking dish. Spoon the turkey-spinach mixture evenly into each boat, packing gently.
08 - Sprinkle the remaining mozzarella and Parmesan cheese over the tops. Bake for 20–25 minutes until zucchini is tender when pierced with a fork and cheese is golden and bubbly.
09 - Remove from oven and let rest for 5 minutes. Garnish with additional fresh herbs if desired. Serve warm while cheese is still melted.