Preheat oven to 350 degrees F. Cream together sugar, butter and shortening. Add eggs, one at a time, beating well after each addition. Add flour and Fresca alternately. Add baking powder and when mixture is fully creamed, add vanilla and fruit rinds. Pour into greased and floured 9 X 13-inch Cake Pan. Bake 1 hour or until cake tester comes out clean. Frosting: Mix all ingredients except cherries and beat constantly while heating in the top of a double boiler. When thoroughly mixed, thick, and spreadable, frost cake. Decorate top of cake with chopped maraschino cherries. Note: Since Fresca is available only in limited areas if at all, 7-up may be a good substitution, or any lemon-lime drink. Also, since the problem with the cherries has been resolved with a different food coloring, you may use the new ones or use gum drops instead for the garnish. Syrup from a can of dark cherries might be substituted for the Maraschino cherry syrup.