Preheat oven to 350°F. Take a rimmed baking sheet and line it with a Silpat baking mat or parchment paper.
Set out a 9x13” glass baking dish and pour tomato sauce into it, making sure it is spread in a thin layer that covers the bottom. Set baking dish aside.
To a large glass bowl, add the following ingredients: ground turkey, eggs, Parmesan cheese, oregano, basil, parsley, garlic, onion salt, and red pepper flakes. Season this mixture with salt and black pepper to taste.
Use your hands to thoroughly combine the mixture. Then divide it into 24 equal-sized portions (18 if you prefer larger meatballs). If necessary, add more Parmesan cheese to bind the ingredients.
Gently roll each portion into a ball, then place each meatball onto the prepared baking sheet. Leave room between each meatball. Place baking sheet into the pre-heated oven and bake for 15-20 minutes.
Remove the baking sheet from the oven and transfer the meatballs to a prepared baking dish. If desired, drizzle with additional tomato sauce and Parmesan cheese.
Place the baking dish in the oven for about 10 minutes, or until the meatballs and sauce are heated through. Remove from oven and serve immediately. If desired, add additional tomato sauce, Parmesan cheese, and fresh basil.