First, cook the spaghetti squash: Preheat the oven to 400 F. Use a chef's knife to cut the spaghetti squash lengthwise from stem to tail. Spaghetti squash are really tough and hard, so be cautious and work slowly.
Use a soup spoon to scrape out the seeds and stringy bits of flesh from inside the
squash, and discard them. The inside should look clean and fairly smooth. Place the squash halves cut-side down in a roasting pan. Pour a little water into the pan, enough to cover the bottom. Your squash will roast just fine without it, but I find that the water helps the squash steam and become more tender.
Transfer the squash to the oven and cook for 30 to 45 minutes. Smaller squash will cook more quickly than larger squash. Check the squash after 30 minutes to gauge cooking.
The squash is ready when you can easily pierce a fork through the flesh all the way to the peel. The flesh will also separate easily into spaghetti-like strands. You can also taste it right now — if the noodles are still a bit crunchy for your taste, put the squash back in the oven for another 15 to 20 minutes.
Use a fork to gently pull the squash flesh from the peel and to separate the flesh into strands. The strands wrap around the squash horizontally — rake your fork in the same direction as the strands to make the longest "noodles.”
To make the sauce: Heat the olive oil in a large skillet over medium heat. Add the onion and garlic, and sauté until translucent, about 5 minutes. Add the carrot and celery, and sauté until the vegetables are tender, about 5 more minutes.
Add the ground turkey, salt and pepper, and cook, stirring occasionally, until the turkey is no longer pink, about 5 minutes.
Add the crushed tomatoes and dried oregano. Bring the sauce to a simmer, and cook, stirring occasionally, until it begins to thicken, about 15 minutes. Stir in the basil. Season the sauce to taste with salt and pepper.
Serve over the spaghetti squash, topped with grated parmesan if desired.
Adapted from Turkey Bolognese by Giada De Laurentiis at http://www.foodnetwork.com/recipes/giada-de- laurentiis/turkey-bolognese-recipe-1944775, and “How to Cook Spaghetti Squash in the Oven” by Emma Cristensen (The Kitchn) at http://www.thekitchn.com/how-to-cook-spaghetti-squash-in-the-oven-178036