These burgers are filled with onion and topped with melted cheese.
Vegetable oil
Onion, chopped
Ground beef
Egg
Sliced cheese
Lettuce
Tomato, sliced thin
Ketchup
Heat a thin layer of vegetable oil in a frying pan. Add the onion, and fry for about 5 minutes until softened. Remove from the heat and cool.
5 minutes
Combine the ground beef, egg, and cooked onion.
Shape the beef mixture into patties. Cook the burgers on a grill for about 6 minutes, flipping halfway until browned on each side and cooked through.
6 minutes
In the last minute of cooking, lay a slice of cheese on top of each patty. Cover and let the cheese melt slightly.
Lightly toast the hamburger buns. Sandwich the patties in the buns, topping with lettuce, tomato, and ketchup as desired.