3 cuts to cut the round cake into 8 equal pieces

Assuming a round cake is cut from above with three straight cuts, make all three cuts pass through the center and space their diameters by 60 degrees. Each diameter produces two opposite rays, so the three cuts create eight radial sectors, each with central angle 45 degrees and therefore equal area. The key is that every cut crosses the center; parallel cuts produce unequal regions. If the intended puzzle permits only sequential stacking or requires equal volume in a non-flat cake, ask for that clarification because the construction depends on the standard planar-cut interpretation.