In a large skillet, melt a tablespoon of butter over medium heat. Add thinly sliced onions and sauté for about 10-15 minutes, stirring occasionally until they turn golden brown and soft.

Once the onions are caramelized, push them to the side and add one pound of ground beef to the skillet. Cook for about 5-7 minutes until the beef is browned and no longer pink.

Stir the caramelized onions into the browned beef, then pour in a few tablespoons of gluten-free soy sauce. Season to taste and cook for another 2-3 minutes.

Reduce heat to low, sprinkle shredded cheese over the mixture, cover, and let sit for 2-4 minutes until cheese melts.

Lightly toast buns in another skillet for about 2 minutes, then spoon the cheesy beef mixture onto the buns and serve immediately.