Heat oven to 400 degrees. Slice spaghetti squash in half lengthwise and scrape out the seeds. Rub 1/2 tablespoon olive oil onto the cut side of squash and season with salt and pepper. Place cut side down on a large, rimmed baking sheet and cook for 45 to 60 minutes, until tender all the way through.
Heat 1 tablespoon olive oil in a large nonstick skillet over medium heat. Add onion and carrot and cook for 2 minutes. Add turkey and garlic and cook until turkey is cooked through, breaking into pieces with a wooden spoon. Season with salt and pepper and add Italian seasoning.
Add tomato paste and crushed tomatoes and stir well to combine everything. Reduce heat and simmer 5-10 minutes. Add red pepper flakes and more salt and pepper if necessary.
Scrape out insides of spaghetti squash with a fork. Serve topped with meat sauce and Parmesan cheese.
Notes
Cook the spaghetti squash until tender, but careful not to overcook. It will get mushy.