01 -
In a skillet, heat olive oil over medium-low heat. Add onions, season with salt and pepper, and cook for 20–25 minutes until golden and soft. Set aside.
02 -
In a bowl, mix ground beef, ketchup, Worcestershire sauce, onion powder, salt, and pepper. Form into 4 patties slightly larger than the bread slices.
03 -
In a cast-iron skillet, melt 2 tablespoons butter over medium heat. Cook patties for 4–5 minutes per side until browned. Remove and set aside.
04 -
Wipe the skillet clean and melt the remaining butter. On 4 slices of rye bread, layer one patty, caramelized onions, 2 slices of Swiss cheese, and top with another slice of bread.
05 -
Grill sandwiches in the skillet over medium heat for 2–4 minutes per side, pressing gently, until the bread is crisp and the cheese is melted.