We’re about a month out from Camille’s birthday, and we’ve settled on a rainbow themed girl’s birthday party. We are so excited! While I’m making these easy rainbow cookies for the goodie bags, I’ll keep the frosting bag out for this mini rainbow cake. If you make the rainbow cookies, you’ll have about half of the frosting leftover, which is just enough for making this rainbow cake recipe! So perfect, right? No one needs to know that this birthday party requires only one bag of frosting! This rainbow cake is really just my easy mini vanilla cake with some piped rainbows and mini marshmallows. Easy, right?
Cake decorating is not one of my strengths, though you probably think it would be, since baking is my career. I don’t really have an answer as to why I can’t decorate a cake to save my life; maybe it’s because I’m not a perfectionist? Or, because I drink too much coffee and tea? I chill the cake very well before piping the rainbows, because if they come out wonky, it’s easy to scrape the rainbows off a cold cake and start over. If the buttercream coat is the same temperature as the rainbows, they can smear together.
So, chill your cake very well first before attempting to pipe the rainbows. I pipe them at an upwards angle because my hands were too shaky to pipe perfect full rainbows. Maybe caffeine is responsible for my inadequate cake decorating skills after all. I finish the cake with mini marshmallows at the end of each rainbow, and gold glitter sprinkles. Camille could hardly contain her excitement on recipe testing day for this cake, and she loved every bite. She picks the marshmallows off first, of course, and requests a slice with at least two rainbows on the end. I can’t say I blame her. Rainbows are just so fun!
A few helpful hints for this rainbow cake recipe:
-I used a Wilton 105 tip. Be sure to see my rainbow cookies post for a detailed explanation how to build the frosting bag for the rainbow swirl buttercream. -If you make the rainbow cookies, you’ll have enough leftover frosting to make this cake–no need to double the recipe! -First, frost the cake with a thin layer of buttercream, ignoring any crumbs; this is called a crumb coat. Chill the cake for 30 minutes. Then, frost the cake with a final thicker layer of buttercream. -Chill the cake for an hour before piping on the buttercream rainbows. You’ll thank me if you have to re-do any rainbows. -Mini marshmallows serve as clouds, and gold glitter sprinkles are fun! -Let the cake sit out for an hour at room temperature before serving so the buttercream softens.
*Notes: make-ahead tips are within the recipe; please read through. Cake and frosting can be made ahead of time. Cake can be frozen (tightly wrapped in plastic wrap for up to 1 month; defrost in fridge fully before frosting). Frosting can be made ahead of time and kept in the fridge for up to 1 week.
