Place raisins in a small bowl; add boiling water to cover. Let stand 15 minutes. Drain well, and set aside.
Beat shortening at medium speed of an electric mixer until creamy; gradually add brown sugar, beating well.
Add eggs, one at at time, beating after each addition.
Combine flour and next 5 ingredients; add to the shortening mixture alternately with pureed mango, beginning and ending with the flour mixture. Stir in the reserved raisins.
Pour the batter into a greased and floured 13x9x2 inch pan. Bake at 325 degrees for 50 minutes or until a wooden toothpick inserted in the center comes out clean. Cool completely in the pan on a wire rack.
For the icing:.
Beat butter at medium speed of an electric mixer until creamy. Gradually add the sugar, beating until blended. Add the water and lemon rind, beating until it reaches spreading consistency.