Butter one side of each slice of bread. Lay two slices of bread, butter side down.
Add two slices of cheese on top of each slice of bread and follow with the sliced turkey, red pepper strips, and caramelized onions. Top with the remaining cheese and the final slice of bread, butter side up.
Place (one sandwich at a time) in the fryer basket of an air fryer and cook for 5 minutes at 350-degrees.
Flip the sandwich. Increase the temperature to 400 and cook the sandwich for an additional 1-2 minutes until golden brown. If desired, flip the sandwich and cook again for an additional 1-2 minutes to brown both sides.
Continue the same steps with the second sandwich.
Serve and enjoy.
This grilled cheese sandwich can also be made in a skillet.
Continue with the same instructions but heat a skillet to medium-high heat and cook the sandwich on both sides until golden brown.