Pistachio cake

From Memory Alpha, the free Star Trek reference

Pistachio cake is a type of dessert using pistachios.

In 2376, Tuvok prepared a pistachio cake with pera-cream sauce, Kathryn Janeway's favorite, after losing his memory due to a Ba'neth weapon. After being asked about the cloaking frequency of the Ba'neth, he was unable to remember but was able to reproduce a rough likeness of the graph he saw on the cake. This allowed the USS Voyager crew to track down the Ba'neth. (VOY: "Riddles")