When listing ingredients on a food label for cake with frosting, do you include the frosting in the list or make a separate label for that? also, would the label read "Cupcakes with Butter Cream Frosting" or just " Vanilla cupcakes" ? 

I rarely sell cakes and do not list ingredients when I do, but my first thought is that all the ingredients should be listed as one unit, not separated into cake and buttercream.  As to how you label the product, Cupcakes with Buttercream Frosting or Vanilla Cupcakes, is a personal choice, either would work.

You really need to ask your health department what is required   I would list cake separately then the icing