I have a habit of starting a recipe with one flavor inspiration, then piling on one after another, and usually end up with a recipe five flavor layers deep. (faring-well.com)
I'm sure the frosting is delicious without the orange, but with it, you are adding another subtle flavor layer that really works well with the cake. (epicurious.com)
Chocolate and coffee flavored layer cake filled with delicious chocolate - coffee buttercream filling and covered in decadent chocolate fudge frosting. (easydessert.org)