Preheat oven to 350 degrees F. Grease bottom of a 13x9x2-inch baking pan; set aside. In a large mixing bowl beat the 1/2 cup butter with an electric mixer on medium speed for 30 seconds. Add granulated sugar and vanilla; beat until light and fluffy. Add eggs, one at a time, beating 1 minute after each. Combine flour, baking powder, and salt. Alternately add flour mixture with cream of coconut and milk to batter, beating on low speed after each addition just until combined. Spread batter into prepared pan.
Bake about 25 minutes or until a wooden toothpick inserted in center comes out clean. Cool thoroughly in pan on a wire rack.
For frosting, in a medium mixing bowl beat together the 1/3 cup softened butter and the powdered sugar. Gradually beat in orange peel and enough juice to make of spreading consistency. Spread frosting over cake. Sprinkle with toasted coconut. Makes 12 to 16 servings.