Preheat a gas grill over high heat or a charcoal grill until it glows bright orange and ashes over.

While the grill preheats, divide and shape the ground beef into 6 patties. Brush the burgers lightly with oil.

Grill the burgers until browned and slightly charred on the first side (about 3-4 minutes). Flip the burgers over and continue to cook until desired doneness - about 4 minutes for medium-rare, longer for a more done burger. Drizzle burgers with Bourbon Whiskey BBQ Sauce and place one slice of cheese on each burger. Cook an additional minute or until the cheese just begins to melt. Remove from the heat and set aside while you assemble the burgers.

To assemble the burger, spread the cut side of both parts of the bun with 1 tbsp. mayonnaise on each half. Place Onion Rings on top of the cut side of the bottom bun portion. Add the burger with sauce and cheese. Top with tomatoes and lettuce. Replace the top bun over the top of the sandwich. Serve!