Not really answering your question, but, I've seen it as Lobster, not cake, which given the nature and cost of the foods in question makes more sense.

Really, I think the holiday is all about spoiling your significant other(s) in a more direct, less frilly way than Valentines Day, from the posts I have seen on it.

Makes me wonder how long until the Surf N'Turf holiday shows up...but then, that may be what 40% of the population considers date night...