01 - Cook turkey bacon in a skillet over medium heat until crispy, approximately 4-5 minutes per side. Transfer to paper towel-lined plate to drain excess grease.
02 - Toast all bread slices until golden brown. Optionally spread each slice lightly with softened butter while warm for enhanced flavor.
03 - Spread mayonnaise and Dijon mustard evenly on one side of each toasted bread slice, ensuring full coverage to the edges.
04 - Place first bread slice mayo-side up. Layer with half the lettuce leaves, distribute half the turkey breast evenly, and arrange tomato slices. Season lightly with salt and pepper.
05 - Place second bread slice mayo-side down onto the stack. Spread mayo on top side. Layer with half the cooked turkey bacon, additional lettuce, tomato slices, and red onion if desired.
06 - Finish with third bread slice mayo-side down. Press gently to compact layers, then secure with toothpicks at each corner.
07 - Slice diagonally into halves or quarters. Repeat assembly process for second sandwich. Serve immediately while bread remains crisp.