Lightly spray one side of tortilla with olive oil. Lay the tortilla, oil side down, in the air fryer basket. (You could replace olive oil with butter if you prefer.)
Sprinkle one side with cheese being sure not to add too much cheese. (If you are adding something like cooked chicken or beef, start with a thin layer of cheese, a layer of the filling, and then a little more cheese.)
Fold the tortilla in half and place 1-2 toothpicks in the center to help keep it closed. Cook at 350 degrees F for 3 minutes, remove toothpicks, flip the quesadillas over and cook another 2-3 minutes or until cheese is melted.
