- In a small bowl, toss together the onion, vinegar, and 1/4 teaspoon each salt and pepper. Let sit, tossing occasionally, until ready to use.
- Heat grill to medium-high. Gently form the beef into 4 balls. (Don’t overwork the meat — this can result in a tough, dry burger.) Flatten each ball into a 3/4-inch- thick patty. Using your thumb, make a shallow 1 1/2-inch-wide indent in the top of each patty. Season the patties with 1/2 teaspoon each salt and pepper.
- Place the patties on the grill, indent facing up, and cook until the burgers release easily from the grill, 3 to 4 minutes. Flip and cook to desired doneness, 3 to 4 minutes more for medium. During the last 2 minutes, top with the blue cheese and grill, covered, until gooey.
- If desired, grill the buns until lightly toasted. Serve the burgers on buns and top with the cut of balsamic onions, lettuce, tomato, and bacon, if desired.
A recipe shared from Delish