1Arrange bacon slices in a single layer in a cold skillet. Turn heat to medium and cook bacon, flipping occasionally, until deeply golden and completely crisp, about 10-12 minutes. Transfer cooked bacon to a paper towel-lined plate and pat thoroughly to remove excess grease. Set aside.
2Spread butter evenly on one side of each bread slice. Place bread slices butter-side down in a clean skillet over medium heat. Toast until light golden brown with a slight crunch, about 2-3 minutes per side. Remove from heat and let cool slightly for 30 seconds.
3Place both toasted bread slices on your work surface, toasted side up. Spread 1 tablespoon of mayonnaise evenly on each slice, covering all the way to the edges to create a moisture barrier.
4Layer crisp lettuce leaves on one slice of bread, arranging them to cover the entire surface. Place tomato slices on top of lettuce in a single layer. Season tomatoes generously with salt and black pepper to taste.
5Stack all 6 bacon slices on top of the seasoned tomatoes, arranging them in a slightly overlapping pattern for even distribution.
6Place the second bread slice on top, mayo-side down. Press gently to compress the sandwich slightly.
7Using a sharp serrated knife, cut the sandwich diagonally from corner to corner, creating two triangular halves. Secure each half with a decorative toothpick if desired for restaurant-style presentation.