Spike and Luna share something, younger siblings of the princess (even if Luna was one too) and always ignored in favor of their siblings, so they decided to try to do something by themselves, withouth thinking of their siblings and enter into a dessert contest!...And no, Luna trying to make plans with Celestia and being rejected because of that same contest had nothing to do with it!

This take place on the same universe of "A Not-So Draconian Adventure", but is not really related to it
https://www.fimfiction.net/story/547435/a-not-so-draconian-adventure