To prepare the patties, divide the beef into 4 portions, lightly shaping each into patties and sprinkle with salt.
Cover and refrigerate 30 minutes.
To make the sauce, combine mayonnaise, mustard, and ketchup and set aside.
Cook bacon in a nonstick skillet over medium-low heat until crisp. Remove bacon from pan with a slotted spoon.
Add onion to drippings in pan, cook 15 minutes or until golden brown.
Combine bacon, onions, chives, Worcestershire sauce, and pepper in a small bowl.
Heat cast-iron skillet over medium-high heat.
Add patties; cook 2-4 minutes on each side until done.
Spread 2 teaspoons sauce on bun. Add patty, onions, a tomato slice and lettuce.