Preheat oven to 400°. Line a rimmed baking sheet with parchment paper or aluminum foil.

Add bacon in a single layer and bake for 20 minutes or until crispy.

Remove to a paper towel lined plate.

Spread butter onto one side of each slice of bread.

Place a griddle or skillet over medium-high heat and place bread, butter side down onto the griddle.

Top 2 slices with cheese and add top each with a slice of bread, butter side up.

Flip the grilled cheese sandwiches to toast on both sides. Flip the single slice of bread to lightly toast on both sides.

Remove to a wire rack.

Spread mayonnaise on the toasted bread, top with lettuce, tomato and bacon.

Spread mayonnaise onto one side of grilled cheese and place over the bacon.

Slice at a diagonal with a sharp knife and serve immediately.