Brush burger patties with barbecue sauce and grill them on high heat for about 3 minutes on each side.
Slice the buns and grill sliced-side down for a few seconds to char the bread.
To assemble, spread the buns with any desired optional condiments. Layer each bun with 2 lettuce leaves,1 slice tomato, a few slices red onion, 2 slices cheddar cheese and the burger patty.