Divide the beef into 2 or 3 pieces and form into a ball, then flattened into ¾ inch thickness. Season with garlic salt and black pepper.
Preheat a medium nonstick pan over medium low heat to medium heat then add the onions. Cook until caramelized about 45 minutes. Season with salt and pepper. Set aside.
Heat olive oil in a different pan and cook the burgers about 4 to 5 minutes per side. Top with cheese and cook until starts to melt.
Top burger with the caramelized onions. Serve
Recipe by The Gluten Free at https://www.theglutenfree.com/gluten-free-caramelized-onion-burger/