In medium bowl, beat 1/4 cup butter and the granulated sugar with electric mixer on medium speed 1 minute. Add eggs, one at a time, beating on low speed after each addition. Alternately add flour mixture, about one-third at a time, and 1/3 cup milk, about half at a time, beating just until blended. Beat in 1 teaspoon lime peel. Stir in mango.