01 - Preheat oven to 400°F. Line a baking dish with parchment paper or lightly grease it with olive oil.
02 - Slice each zucchini in half lengthwise. Using a spoon, scoop out the center seeds and flesh to create boats, leaving about a 1/4 inch wall. Finely 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 minutes until softened. Stir in the minced garlic and cook for 30 seconds until fragrant.
04 - Add ground turkey to the skillet and cook, breaking it up with a spoon, for 5 to 7 minutes until no longer pink. Season with salt, pepper, dried oregano, and red pepper flakes.
05 - Mix in the chopped zucchini flesh and fresh spinach. Cook for 2 to 3 minutes until the spinach is wilted. Remove from heat and stir in 1/4 cup of basil pesto and half of the chopped fresh basil.
06 - Arrange the hollowed zucchini boats in the prepared baking dish. Generously fill each boat with the turkey and spinach mixture, pressing gently to pack the filling.
07 - Drizzle the remaining pesto over the filled boats. Sprinkle evenly with shredded mozzarella and grated Parmesan cheese.
08 - Bake for 20 to 25 minutes until the zucchini is tender and the cheese is golden and bubbly.
09 - Remove from the oven, garnish with the remaining fresh basil, and serve immediately while hot.