Spread 1 tablespoon of refried beans on half of a tortilla. Place bean-topped tortilla, bean side up in a medium skillet or on a griddle. Sprinkle with one-fourth of the cheese.
Cook over medium heat approximately 3 minutes or until cheese begins to melt. Fold tortilla in half. Turn and cook 1 to 2 minutes more or until golden brown. Repeat with remaining refried beans, tortillas, and cheese.
To serve, slice each quesadillas into thirds. If desired, serve with salsa.