Classic Patty Melt

Directions

1. Season ground beef with salt and pepper and divide into 3 equal-sized balls. Shape each ball as close as possible to the shape of the bread. Make an indentation in the center of each patty with your thumb.
2. Melt butter in a skillet over medium heat and cook onion until soft and translucent, 5 to 8 minutes. Remove from the skillet and divide into 3 equal portions. Place beef patties into the same skillet and cook until desired doneness, 3 to 5 minutes per side.
3. Meanwhile, spread 1 teaspoons mayonnaise on one side of each slice of bread.
4. Place bread mayonnaise side-down in the skillet. Top with 1 slice of cheese, 1 beef patty, 1/3 of the onions, a second slice of cheese, and another slice of bread, mayonnaise side up. Cook bread until golden brown and cheese has started to melt, 3 to 4 minutes. Flip each sandwich over and cook an additional 3 to 4 minutes.