Sautee, grill or make the caramelized onions in the air fryer. Follow this easy recipe for the air fried version. Set aside for now. Preheat the air fryer to 375 degrees for 5 minutes.
Chop and mince the garlic clove and combine with softened butter in a bowl.
Spread garlic butter on one side of the each slice of bread.
In a bowl, season the ground beef with salt, pepper and granulated garlic.
Shape the ground beef into patties, placing them next to the bread to ensure they are of similar shape and just a tiny bit larger than the bread. They will shrink during the cooking process.
Transfer the patties to the air fryer and cook at 375 degrees F for 8-11 minutes, flipping half way. Cooking time will vary depending on personal preference for doneness. For very well done burgers, you may need to cook for up to 15 minutes.
Place a slice of cheese on top of the bread (the side without butter), transfer the burger patty and add on top of the cheese.
Top with another slice of cheese, caramelized onions and another slice of bread, butter side up.
Transfer the patty melt to the air fryer, butter side down. For the slice of bread on top, make sure the buttered side is facing up.
Air fry for an additional 6-7 minutes at 375 degrees F, flipping the patty melt halfway through.
Serve with patty melt sauce and chips on the side.