INGREDIENTS
1 medium onion, chopped
1 tablespoon canola oil
2 tablespoons ketchup, divided
2 tablespoons low-fat mayonnaise
2 teaspoons dill pickle relish
1 teaspoon distilled white vinegar
1 pound lean (90% or leaner) ground beef
2 tablespoons Worcestershire sauce or steak sauce
1/2 teaspoon freshly ground pepper
4 sesame-seed or other hamburger buns, toasted
4 slices tomato
4 leaves green-leaf lettuce
DIRECTIONS
1.Preheat grill to medium-high (or see Stovetop Variation).2.Combine onion, oil and 1 tablespoon ketchup in a medium saucepan. Cover and cook over medium-high heat, stirring often, until the onion is softened, 5 to 7 minutes. Reduce heat to medium-low, uncover and cook, stirring occasionally, until very soft, 5 to 8 minutes more. Transfer to a medium bowl and let cool for a few minutes.
3.Meanwhile, combine the remaining 1 tablespoon ketchup, mayonnaise, relish and vinegar in a small bowl. Set aside.
4.Add beef, Worcestershire (or steak sauce) and pepper to the onion and gently combine without overmixing. Form into 4 patties, about 3/4 inch thick.
5.Oil the grill rack (see Tip). Grill the burgers, turning once, until an instant-read thermometer inserted in the center registers 165°F, 4 to 5 minutes per side.
6.Assemble the burgers on toasted buns with the ketchup-mayonnaise sauce, tomato slic