To split a cake into layers, place it on a flat work surface and use a long, thin serrated knife. Working carefully and evenly, score the cake horizontally all the way around the perimeter, cutting about an inch into the cake at the point at which you want to split it. Once the entire cake is scored, place the knife into the scored groove and, using a sawing motion, slowly start cutting at the same time you rotate the cake. If you follow the groove and continue to rotate the cake, you will eventually cut all the way through. If you have a revolving cake stand or a lazy Susan, use it to make rotating the cake easier.