This one was heard on the Animal Planet tv show, Treehouse Masters. Daryl, the foreman, was referring to a door on the treehouse that looked like a sarcophagus. It is a congruent conflation of “icing on the cake” and “cherry on top”, both meaning an extra enhancement to something. There are certainly cherries that appear on the top of some cakes, but not as common as sundaes. In fact there is a Quebec idiom, “la cerise sur le sundae”, also with the same meaning but the cherry is on the sundae, not cake. A shout out to my high school buddy, Marti Fenimore, for sending this one in!