Follow these simple steps to create a delicious Classic Patty Melt:

1. Caramelize Onions: In a skillet, melt 1 tablespoon of butter over medium heat. Add sliced onions, season with salt, and cook until golden brown (about 10-15 minutes). Stir occasionally and set aside.

2. Form Patties: Meanwhile, divide the ground beef into 4 equal portions and shape them into patties. Season both sides with salt and pepper.

3. Cook Patties: In the same skillet, increase the heat to medium-high. Add the beef patties and cook for 3-4 minutes on one side.

4. Flip Patties and Add Cheese: Flip the patties and place a slice of Swiss cheese on top of each patty. Cook for another 3-4 minutes, ensuring the cheese melts.

5. Prepare Bread: While the patties are cooking, butter one side of each slice of rye bread.

6. Assemble Sandwiches: On the unbuttered side of two slices, layer the cooked patty with Swiss cheese, followed by a generous helping of caramelized onions. Top with another slice of bread (buttered side out).

7. Grill Sandwiches: Return the sandwiches to the skillet, cooking until golden brown on both sides, about 3-4 minutes per side.

8. Serve: Once grilled and crispy, remove from the skillet and allow to cool slightly. Cut in half and serve warm.