When it's time to frost a cake, there is one major enemy you need to look out for: crumbs. This simple practice will keep your cake layers intact, and keep crumbs from invading your pristine frosting. Photo by Sarah Sphar.
As Sheela Prakash at The Kitchn explains, trying to frost a cake right after its done baking is a recipe for disaster. Even if you let it cool down to room temperature, there's still a good chance you'll make a crumby mess out of your cake. To avoid that, wrap each layer of cake in plastic wrap and stick them in the fridge for at least a couple of hours (overnight if possible). Once the layers are chilled, you can trim them as needed and carefully apply a layer of frosting without worrying about crumbs. If you want apply more frosting, or plan to decorate the cake, it doesn't hurt to stick the cake back into the fridge for another 15 minutes beforehand. Chilled cake is manageable cake.