01 - Cook bacon in a skillet over medium heat until deeply browned and crisp. Transfer to paper towels to drain.
02 - Evenly spread softened butter on one side of each bread slice.
03 - Preheat a large non-stick skillet or griddle over medium-low heat.
04 - Place two bread slices, buttered side down, onto the hot surface. Layer each with one slice of cheese, two bacon slices, tomato slices, and lettuce. If desired, spread a thin layer of mayonnaise and season with black pepper.
05 - Top with remaining cheese slices and cover with the other bread slices, buttered side up.
06 - Cook for 3 to 4 minutes per side, gently pressing with a spatula, until exterior is golden brown and cheese is thoroughly melted.
07 - Remove sandwiches from skillet. Allow to rest for 1 minute, then slice and serve immediately.