I think the diagram should be several dotted rays emanating from the
same point, arranged so that if you cut along the lines, each piece will
have the same volume of cake and of frosting.  It is an impressive diagram
when the number of pieces is a not too small odd number  such as 5, 7, or
9.

(There is also an interactive n player version.)

Gerhard "Save A Piece For Me" Paseman, 2012.12.29