1Caramelize the red onion in a pan with butter, salt and paprika.
2Prepare the sauce by mixing chopped cornichons, ketchup, mustard, mayonnaise, and paprika in a bowl.
3Slice the tomato and prepare the lettuce leaves.
4Season the ground beef with salt and pepper, form into patties and flatten them with the bottom of a small pan in a hot frying pan to obtain a caramelized crust.
5When turning the patties, add a slice of cheddar cheese to each one to melt it.
6Toast the burger buns in the pan.
7Assemble the burger: spread the sauce on the bottom bun, add the beef patty with the melted cheese, lettuce, tomato, caramelized onions, and top with the other bun.
8Use a blowtorch to melt the cheddar cheese further.