Place a small griddle insert or cast iron pan into the grill and prepare the grill for Direct Medium Heat cooking (375°–425°F). Preheat for 15 minutes and brush the grill grates clean.
Place a small griddle insert or cast iron pan into the grill and, if available, set the grill to Manual Mode level 6 (otherwise set the grill to 400°F). Preheat for 15 minutes and brush the grill grates clean.
Form the beef into six 3/4"-thick patties of equal size. Press a shallow, 1"-wide indentation into the center of each patty with your thumb or the back of a spoon (this helps prevent the patties from puffing up as they cook). Refrigerate the patties until ready to grill.
Cook the bacon on the griddle insert until crisp, 10–12 minutes, flipping halfway through. Transfer the bacon to paper towels to drain.
Adjust the grill to Direct Medium-High Heat cooking, 450°–500°F. Season both sides of the patties with kosher salt and black pepper.
Adjust the grill to 500°F. Season both sides of the patties with kosher salt and black pepper.
Grill the patties, with the lid closed, for 5 minutes. Flip the burgers and cook until the internal temperature reaches 155°F, about 4 minutes longer.
Top each patty with two slices of cheese and place the buns on the grill to toast for about 1 minute.
Top each burger with bacon, and serve the burgers with lettuce, tomato, onion, and your favorite condiments.
