Speedy Skillet Patty Melts

Melt 1 tablespoon of unsalted butter and 1 tablespoon of olive oil in a large cast-iron skillet over medium-low heat. Add 1 medium thinly sliced yellow onion and cook, stirring occasionally, for 15-20 minutes until deeply caramelized and tender. Season with 1/4 teaspoon salt. Remove onions from skillet and set aside.

While onions cook, divide 1 pound of ground beef into two equal patties, about 1/2-inch thick. Season both sides with the remaining 1/4 teaspoon salt and 1/4 teaspoon freshly ground black pepper.

Increase skillet heat to medium. Add patties to the hot skillet and cook for 3-4 minutes per side for medium-rare, or longer to your desired doneness. Remove patties from skillet and set aside.

Reduce heat to medium-low. Add the remaining 1 tablespoon of unsalted butter to the skillet. Place 2 slices of rye bread in the skillet. Top each slice with 2 slices of Swiss cheese, then one cooked beef patty, and a generous portion of the caramelized onions. Top with the remaining 2 slices of rye bread.

Grill the patty melts for 3-5 minutes per side, or until the bread is golden brown and crispy, and the cheese is thoroughly melted and gooey. Press gently with a spatula to ensure good contact with the skillet.

Remove from skillet, slice in half, and serve immediately.