01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with cooking spray or oil.
02 - Bring a large pot of salted water to boil. Cook pasta until al dente according to package directions. Drain well and set aside.
03 - Heat a large skillet over medium heat. Add ground turkey and cook for 6-7 minutes, breaking apart with a spoon, until browned and fully cooked.
04 - Add diced onion, garlic, and red bell pepper to the skillet with the turkey. Sauté for 4-5 minutes until vegetables are softened and fragrant.
05 - Stir in chopped spinach and cook for 1 minute until just wilted.
06 - Pour in marinara sauce, tomato paste, Italian seasoning, red pepper flakes, salt, and black pepper. Stir well and simmer for 3-4 minutes to meld flavors.
07 - Add cooked pasta to the skillet with the turkey sauce. Mix in half of the mozzarella and half of the Parmesan until well combined.
08 - Transfer the pasta mixture to the prepared baking dish. Spread evenly and sprinkle remaining mozzarella and Parmesan over the top.
09 - Bake uncovered for 20-25 minutes until cheese is completely melted and bubbling around the edges.
10 - Remove from oven and let rest for 5 minutes. Garnish with fresh basil or parsley and serve warm.