Preheat an air fryer to 375 degrees F (190 degrees C). Grease an 8-inch pie pan with cooking spray and set aside.
Combine spinach, cottage cheese, eggs, feta cheese, flour, butter, garlic, onion powder, and nutmeg in a bowl. Stir until all ingredients are well incorporated. Pour into the prepared pie pan.
Air fry until the center is set, 18 to 20 minutes.