Preheat your air fryer to 360°F (182°C) and lightly grease the basket with non-stick spray.
In a large mixing bowl, gently mix together the ground turkey, shredded onion, Dijon mustard, minced garlic, chopped parsley, onion powder, Italian seasoning (if using), salt, and black pepper. Be careful not to mix too much, as this can make the burgers tough.
Divide the mixture and shape it into 4 burger patties, each about 1/2-inch thick.
Carefully place each burger into the preheated air fryer basket, making sure they are evenly spaced and not overlapping. If your air fryer is small, you might need to do this in two batches.
Air fry the burgers for a total of 10 to 13 minutes, flipping them halfway through. Make sure the internal temperature of each burger reaches 165°F (74°C) to ensure they are fully cooked. Overcooked turkey burgers can become dry.
Cheese Burgers: If you are adding cheese, place one slice of cheese on top of the turkey patty in the last 1 minute of air frying.
Toasting the Buns: If you're serving the burgers with buns, you can toast them in the air fryer once the burgers are done. Lightly butter the buns and air fry them at 300°F (149°C), cut side up, for 3 to 4 minutes until they're golden. Alternatively, you can toast the buns in a toaster oven or on the stovetop.
Assemble your burgers by placing the cooked patties on the buns. You can also serve them in lettuce wraps or on a bed of salad for a low-carb option. I top mine with thinly sliced red onion, lettuce leaves, sliced tomato, and cheddar cheese. Enjoy!