Preheat oven to 400 degrees. Using a fork, scoop the flesh out of the skin of the squash, separating it into strands of "spaghetti". Add the spaghetti squash strands to a nonstick pan over medium heat with salt and pepper (to taste), ½ tsp Italian seasoning, and ½ tsp garlic powder, stirring until the seasonings are distributed evenly. Cover and cook for about 5 minutes until the lid is steamy, then remove the lid and cook an additional 5. This will help further soften the squash and get out any excess moisture. You can skip this step if you don't mind the texture of spaghetti squash, but you might have a little extra liquid on your pizza.
Meanwhile, combine all of the * ingredients in a sauce pan. Bring to a boil and reduce to a simmer, cooking for 20 minutes. Let cool slightly and then blend until smooth.
Spritz a baking sheet with nonstick spray and roll out the pizza dough. Spritz the dough with nonstick spray and add a generous sprinkle of garlic powder to the crust. Measure ¼ c of the tomato sauce and spread over the pizza crust.
Set aside another ¼ c of sauce and toss the remaining with the spaghetti squash. Evenly distribute the saucy squash over the crust.
Cut the meatballs in half and arrange on the pizza. Dollop a small amount of the reserved sauce on top of each meatball so they don't dry out. Sprinkle the pizza with cheese.
Bake for 17 minutes, until the crust is cooked.
Notes
A thin crust pizza dough will not be able to support all the toppings. If you want to roll your dough extra thin, you'll need to fork and knife your pizza. The ingredients marked with * can be swapped out for approximately 1½ - 2 c premade pasta or pizza sauce. For the cheese, I also like a mix of ¼ c parmesan cheese with ¼ c mozzarella. Vegan cheese substitutes nicely to make a vegan pizza. Nutritional estimate uses linked recipes. Will vary based on meatball and pizza crust selection. For make ahead tips, see the last paragraph of the blog post.