In a small bowl, combine the ground peppercorns, mayonnaise, and lemon juice. Mix well until the black pepper is evenly distributed throughout the mayonnaise and set the aioli aside.

Cut the avocado in half, remove the pit, and slice the avocado into thin, even slices. Slice the tomato into thin rounds and lightly salt before setting them aside on a plate.

Lay out the sourdough bread slices on your work surface. On one side of each bread slice, spread the prepared black pepper aioli.

On the aioli-covered side of one bread slice, add the turkey slices, followed by the sliced avocado, tomato, mixed greens or lettuce, and a handful of alfalfa sprouts. Add a layer of sharp cheddar cheese on top of the sprouts.

Place the other bread slice, aioli side down, on top of the layered fillings to complete the sandwich. Then, using a sharp knife, carefully cut the sandwich in half and enjoy!