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

Meanwhile, heat lightly oiled large skillet over high; cook burgers with salt/pep 3 min one side; flip over, cook 2 min, then add 1 slice of 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

Add burgers to buns; top each with caramelized onions + 1-2 tbsp sauce—yum!