In a small bown, with an electric mixer on high, beat the cream cheese and butter until creamy. Turn the speed to medium and gradually beat in the sugar, about 1 cup at a time, just until blended and fluffy. Do not overbeat, as the frosting can become too soft.
Using a wooden spoon, stir in the sour cream, vanilla, and lemon rind. Makes about 3 cups or enough to fill and frost a 3-layer, 9-inch round cake, a 13" x 9" x 2" oblong cake, or 2 1/2 dozen regular-size cupcakes.