In a mixing bowl, combine ground beef with salt, pepper, garlic powder, and onion powder. Mix until just combined and shape into oblong patties.

In a skillet over medium heat, melt 2 tablespoons of unsalted butter. Add onions and a pinch of salt, cooking until golden brown, about 10-15 minutes.

Increase heat to medium-high and add beef patties. Sear for 3-4 minutes on each side until browned, ensuring they reach 160°F internal temperature.

Spread softened unsalted butter on one side of each slice of rye bread, then set aside for assembly.

On a buttered slice, layer Swiss cheese, one cooked patty, and caramelized onions, then top with American cheese and another slice of rye bread, butter-side up.

Grill the assembled sandwiches in the skillet over medium heat for 3-4 minutes per side until golden and crispy.

Let the sandwiches sit for a minute, then cut in half and serve hot with fries or salad.