Originally Posted by
bgriff
It is generally served immediately after the main meal, which can be a lot of food by itself, so you may want to save room
Whether you fly in Suites, First, Business or at the back of the plane: You can actually tell them when you want the cake to be served. Just pay a discreet visit to the galley if you don't want the other person to know. More often than not, crew is actually asking when it's best to serve (and kind of spoiling the surprise moment).