Caramelized Onion Beef Burger

Method

1. Heat olive oil in a skillet over medium heat
2. Add onion slices and cook until softened, about 5 minutes
3. Stir in butter, brown sugar, and vinegar; cook until onions are caramelized, 8-10 minutes
4. Form ground beef into 4 patties and cook on the skillet until desired doneness
5. Place cheese on top of each patty and let melt
6. Toast hamburger buns and assemble with lettuce, tomato, and condiments
7. Serve with crispy onion rings on the side
8. Check that the ground meat reaches 71°C (160°F) throughout before serving.