Step 1: Prepare the Beef Patties
In a mixing bowl, combine the ground beef with salt, pepper, and garlic powder (if using). Shape the mixture into 4 even patties. Be sure not to overwork the meat to keep the patties tender. Set aside.

Step 2: Caramelize the Onions
Heat 1 tablespoon of butter in a skillet over medium heat. Add the sliced onions and cook, stirring occasionally, until golden brown and caramelized, about 15 minutes. Remove the onions from the skillet and set aside.

Step 3: Cook the Beef Patties
In the same skillet, add the beef patties and cook them over medium-high heat for about 4-5 minutes per side, or until they reach your desired level of doneness. Add a little Worcestershire sauce to the patties as they cook for extra flavor. Remove the patties from the skillet and set them aside.

Step 4: Assemble the Patty Melt
Butter one side of each slice of rye bread. On the unbuttered side, place a slice of Swiss cheese. Add a cooked beef patty, followed by a generous portion of caramelized onions. Top with another slice of Swiss cheese and then the second slice of buttered bread, buttered side out.

Step 5: Grill the Patty Melt
Heat the same skillet over medium heat. Carefully place the assembled sandwiches into the skillet and cook for about 3-4 minutes per side, or until the bread is golden brown and the cheese is melted.