This is a marble cake with Cream Cheese Icing. I omitted the orange zest. The decorations are made with Royal Icing. Normally the icing is off white because of the yellow coloring in butter. If you would like the icing to be white it would be good to use butter with out coloring or dyes.
Cream Cheese Icing
1 cup unsalted butter (allow to soften)
2 (8ounce packages) cream cheese (allow to soften)
8 cups confectioners' sugar (sifted)
1 to 2 tablespoons milk
1 teaspoon orange zest (optional)
In medium mixing bowl, cream butter and cream cheese together until smooth. Add sugar 1 cup at a time. Add 1 tablespoon of milk and orange zest after the first 4 cups sugar. Add the second tablespoon of milk at the end of mixing if needed. Mix well. Beat on high until smooth. This icing would be great on carrot cake.
Cake Decorating tip: Do not substitute margin for butter. The margin will cause the icing to be too soft.