How to Make It
Shape beef into 2 (1-inch-thick) patties; sprinkle with pepper and salt. Heat a skillet over medium-high heat. Coat pan with cooking spray. Add patties; cook 3 to 4 minutes on each side.
Add onion to pan; cook 5 to 6 minutes on each side; separate into rings. Cut burgers into bite-sized pieces. Divide romaine, burgers, onion, tomato, and cheese among 4 bowls.
Combine mayonnaise, ketchup, and 2 tablespoons water in a small bowl, stirring with a whisk; drizzle evenly over salads. Lightly crush potato chips with your hands; sprinkle evenly over salads.