You frost cakes while they're still warm
THE RESULT: A crumb-filled layer of frosting.
THE FIX: Even if you’re in a hurry or just eager to dig into a freshly baked cake, it’s worth the wait to let it cool. If you frost too soon after it has come out of the oven, crumbs and pieces of the tender, still-warm cake will speckle the frosting. Let cake layers cool completely before frosting, or freeze the cake overnight. The layers will retain their freshness and be nice and firm for optimal results. Another way to avoid a crumb-filled frosting: Apply a thin layer of frosting—known as a crumb coat—to seal in those crumbs, and allow it to set in the fridge for 15 minutes before applying the rest.