Combine ground beef, salt, and pepper in a bowl. Press ground meat into six oblong patties.
Melt two tablespoons of butter in a medium cast iron pan over medium heat.
Include the onion. Simmer the onion for approximately 35 minutes, stirring now and again, or until it is soft and golden.

Cook the patties in a big cast-iron pan over medium-high heat for approximately 2 minutes on each side, or until they are cooked through and golden brown. Take the skillet off of the burner. After removing the patties to the skillet, clean it out.
Place one piece of bread, one burger, two to three tablespoons of caramelized onions, one slice of cheese, and one more tablespoon of secret sauce on top of each other.
Place another piece of bread on top. Continue with the remaining patties, cheese, caramelized onions, secret sauce, and bread.
Have fun!