Preheat your oven to 375°. Cut each squash in half lengthwise. Scoop out the seeds and set aside. You won't need the seeds for this recipe but you can roast them or discard them. Lightly drizzle extra virgin olive oil over the squash and season with salt and pepper.
Place squash halves, cut side down, on a parchment paper lined baking sheet. Bake for about 40 minutes. Let stand about 10 minutes to cool. When ready, using a fork, scrape the inside of the squash to remove spaghetti-like strands. Place strands on a separate plate and set aside.
Heat a large skillet over medium-high heat. Add 1/2 tablespoon to 1 tablespoon olive oil to pan. Add the garlic; cook for about 30 seconds. Add the spinach; cook for just few minutes, or until the spinach wilts. Remove from heat. Combine the spinach mixture, squash strands, half of the mozzarella cheese in a medium bowl and season with salt and pepper.
Return the skillet to medium-high heat. Add the turkey to the pan and cook for about 4 to 5 minutes or until browned and fully cooked. Add the marinara sauce; cover, reduce heat to medium, and simmer for about 4 minutes. Remove from the heat.
Increase the oven temperature to 425°. Spoon the marinara sauce evenly into the bottom of each squash half. Top evenly with the squash mixture. Sprinkle evenly with remaining mozzarella cheese and the parmesan cheese. Bake at 425° for about 20 minutes.
Optional: Turn up the oven temp to broil (usually 500 degrees; keeping the squash in oven). Broil squash for 1 to 2 minutes or until the cheese is golden brown and bubbly. Remove from the oven and serve. Enjoy!