Heat 1 tsp oil in skillet over medium; thinly slice onion + sauté 8-10 min until browned; season with salt + add 2 tbsp water; cover + cook 3-5 min until softened; set aside

Heat lightly oiled large skillet over high; cook burgers with salt/pep 3 min on one side; flip over; cook 2 min; then add 1 slice cheese to each burger; cover pan + cook 1-2 more min until cooked through; no pink remains + cheese has melted

Toast 2 buns until warm + golden; spread each bun with 2 tbsp sauce; top with a burger + pile on those caramelized onions—looks good!