Place a small nonstick skillet over medium heat until hot. Add shallot; cook until tender, stirring often. Stir in orange rind and, if desired, sherry; remove from heat. Spread mixture in a single layer to cool. Combine shallot mixture, butter, salt, and pepper; cover and chill.
Cook green beans according to package directions; drain. Place beans in a serving dish; spoon butter mixture over beans. Toss beans gently before serving.