01 - Preheat oven to 400°F. Lightly coat a large baking dish with olive oil or nonstick spray.
02 - Slice zucchinis in half lengthwise. Using a spoon, scoop out the center of each zucchini to form boats, leaving about 1/4-inch thick shells. Roughly chop the reserved zucchini flesh.
03 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook for 2 minutes. Add minced garlic and sauté for an additional minute.
04 - Add ground turkey to the skillet. Cook, breaking up the meat with a spoon, until turkey is fully browned and no longer pink, about 5 minutes.
05 - Stir in the chopped zucchini flesh and cook for 2 minutes. Add chopped spinach and cook until just wilted, about 1 minute.
06 - Remove skillet from heat. Stir in basil pesto, salt, black pepper, and dried Italian herbs if using. Mix thoroughly until well combined.
07 - Arrange zucchini boats in prepared baking dish. Evenly distribute the turkey and spinach filling among each zucchini boat.
08 - Sprinkle shredded mozzarella and grated Parmesan evenly over the filled zucchini boats.
09 - Cover dish loosely with foil and bake for 20 minutes. Remove foil and continue baking for 5 to 10 minutes until cheese is golden and zucchini is fork-tender.
10 - Allow zucchini boats to cool slightly before serving.