Directions:
Step 1: Bake the Spaghetti Squash
Preheat the oven to 425 degrees F. Cut the squash in half lengthwise and remove all seeds. Sprinkle with a few pinches of salt, then brush with olive oil. Put the squash, with the cut-side up, on a baking tray and cover with foil. Bake covered for 20 minutes, then continue roasting for an additional 35 minutes.
Step 2: Make the Meatballs
While the squash is roasting, make the meatballs: Blend the celery, carrot, onion, garlic and parsley in a food processor until it makes a paste. Place half of the paste to a bowl; add ground beef, ground pork, eggs, breadcrumbs, parmesan and salt to the bowl and mix by hand. Press the mixture into meatballs (makes 20-25); transfer a baking sheet sprayed with oil. Bake for 10 minutes in the same oven as the squash.
Step 3: Make the sauce:
Heat 3 tbsp of olive oil in a large pot over medium to high heat. Place remaining vegetable paste into the pot and cook for 5 minutes, stirring until the paste looks dry. Add the tomato puree also adding the water to the pot. Stir in basil, oregano and bring to a simmer. Add the meatballs and simmer for 15 to 20 minutes or until meatballs are fully cooked.
Step 4: Scoop out the squash and serve
Scrape the spaghetti squash flesh into strands using a fork and transfer to a large bowl. Season with salt and pepper to taste. Divide the squash among bowls and top each with some meatballs and sauce. Top with parmesan cheese if desired.