Begin by melting 2 tablespoons of butter in a skillet over medium heat. Add one large sliced onion, stirring occasionally, and cook for 10-15 minutes until they become golden brown and soft. Make sure to cover the skillet to keep the onions warm.

In a large bowl, combine 1 pound of ground beef with a splash of Worcestershire sauce, kosher salt, black pepper, and a sprinkle of garlic powder. Mix gently until everything is evenly combined, then form the meat into four equal-sized patties.

Increase the heat to medium-high, and once the skillet is hot, add the beef patties. Sear them for about 4 minutes on one side until browned and crusty, then flip and cook for an additional 4 minutes.

On each slice of your chosen rye or sourdough bread, spread homemade Thousand Island dressing. Then, layer a slice of Swiss cheese, followed by a beef patty, and finish with the caramelized onions.

Butter the outer sides of each assembled sandwich and return them to the skillet over medium-low heat. Grill for about 3-4 minutes on each side until the bread is golden brown and the Swiss cheese has melted.

After grilling, remove the sandwiches from the skillet and allow them to rest briefly. Serve while hot and enjoy.