In a medium-sized skillet, melt 1 tbsp of butter over medium-low heat. Add the sliced onions and 1 tbsp of water and cook for approximately 20 minutes, stirring occasionally, until the onions are golden brown and soft. Once cooked, transfer into a small bowl and set aside.

Season both sides of the beef patty with salt, pepper, and garlic powder. Cook in the same skillet to desired doneness, then place the cooked patty aside. Carefully pour out any excess grease and wipe away any burnt bits.

Spread each slice of bread with a thin layer of mayo.

Over low heat, melt the remaining 1/2 tbsp of butter in the skillet. Place one slice of bread, mayo-side-up to begin toasting. Carefully assemble the sandwich in the pan by layering half the reserved onions, American cheese, cooked burger patty, the remaining caramelized onions, and Swiss Cheese on top. Add the FUNYUNS^® and the remaining slice of bread, gently pressing to close.

Flip the sandwich over and heat until both sides are crisp and toasted, and the cheese is warm and gooey.

Serve alongside an extra handful of FUNYUNS^® and dig in!