Wash and core apples. Place in a 9-inch diameter, microwave-safe baking dish.
In a small bowl, combine raisins, walnuts and sugar. Add butter; use a fork to cream mixture together. Divide stuffing evenly among apples.
Microwave apples on high until apples are tender when pierced with a fork (9 to 11 minutes). Let stand 5 minutes. Serve warm.
Makes 4 servings.