Butter both slices of rye bread and sprinkle with garlic powder. Place one slice of bread butter side down on a non-stick pan.
Top the bread that is in the pan with extra sharp cheddar cheese slices, tomato and roast beef and then cover with the other slice of bread. Sprinkle the top of the sandwich with garlic salt.
Cook both sides of sandwich until golden brown and cheese is melted. Remove from heat pull of the piece of bread closet to the roast beef and on the side that is not grilled layer with mayonnaise. Cut and serve with choice of sides.