The term 'cake portion' can be broken down into three crossword solutions: LAYER (5 letters), PIECE (5 letters), and SLICE (5 letters). A LAYER of cake is a single sheet of cake that has been baked in a flat pan. A PIECE of cake is a single serving of cake, usually cut from a larger cake. A SLICE of cake is a thin, rectangular portion of cake that has been cut from a larger cake. All three terms refer to a portion of cake that is meant to be eaten by one person.