On a cutting board, butter each piece of bread with butter on one side.
Flip the bread over and spread each piece of bread with mayonnaise.
Place the cheese on the buttered side of one piece of bread. Top it with the second piece of bread, mayonnaise side out.
Heat a nonstick pan over medium low heat.
Place the sandwich on the pan, mayonnaise side down.
Cook for 3-4 minutes, until golden brown.
Using a spatula, flip the sandwich over and continue cooking until golden brown, about 2-3 minutes.