Press the beef into a patty and don’t mix or overwork. Salt it lightly.
Cook the patty medium-well on a flat top or griddle and top with a slice of American cheese.
Cover the patties to melt the cheese.
Make the sauce by mixing mayo, ketchup and sweet relish in roughly equal parts.
Toast the buns.
Spread the sauce on the top and bottom buns.
Layer the lettuce, tomatoes, and griddled onions (if desired) on the buns.
