Line a baking sheet with parchment paper and keep it handy. To keep the meatballs warm between batches, preheat the oven to 300 degrees F and line a second baking sheet with parchment paper.
In a large mixing bowl, add the Parmesan, breadcrumbs, parsley, salt, Italian seasoning, garlic powder, onion powder, black pepper, and red pepper flakes. Stir well to combine.
Add the ground turkey. In a small bowl, beat the egg, then add it to the bowl (you also can crack it into an open space in the big mixing bowl and lightly beat it there). With a fork or your fingers, mix lightly just until the ingredients are evenly combined, being careful not to compact the meat.
Portion the meat and shape into 1 1/2-inch meatballs (you will have about 20 total), then arrange them on the first baking sheet.
Preheat the air fryer to 400 degrees F. Generously coat the basket with non-stick spray. Arrange a single layer of meatballs in the basket, ensuring they do not touch so air can circulate (you will need to cook them in batches). Mist the tops with non-stick spray.
Air fry the meatballs at 400 degrees F for 7 to 9 minutes, sliding out the basket and using tongs to gently turn the meatballs over halfway through. The meatballs are done when they reach an internal temperature of 165 degrees F on an instant-read thermometer. When a meatball is cut in half, the meat should look fully cooked.
Place the first batch of cooked meatballs on the second, clean baking sheet, and transfer to the oven to keep warm. Repeat with remaining meatballs.
While the meatballs air fry, warm the sauce on the stove, and prep any other items you’d like to serve them with them. Enjoy the meatballs hot, topped with the sauce, cheese, herbs, and any other additions.
TO STORE: Refrigerate meatballs in an airtight storage container for up to 3 days.
TO REHEAT: Rewarm leftovers on a baking sheet in the oven at 350 degrees F or in the microwave.
TO FREEZE: Place meatballs in a single layer on a baking sheet and freeze until solid. Transfer the frozen meatballs to an airtight freezer-safe storage container or ziptop bag. Freeze for up to 3 months. Let thaw overnight in the refrigerator before reheating.
TO MAKE AHEAD: Prepare the meatballs as directed through Step 4. Place the baking sheet of meatballs in the freezer until solid. Transfer the uncooked frozen meatballs to an airtight freezer-safe storage container or ziptop bag. Freeze for up to 3 months. Cook directly from frozen as directed, adding a few extra minutes to the cook time.