Today I’m sharing a fun St. Patrick’s Day Buttercream Rainbow Cake Tutorial! Of course, this sweet design would work any time of year. Who doesn’t love a rainbow?
If you are familiar with using simple star piping tips, one of the most basic techniques (after the star border) is the shell border. Today’s design incorporates the shell border times 100!
Mainly what I wanted to show you is that you can take a relatively simple technique that you can do well (whether it’s piping dots, stars with the star tip, ruffles, petals, etc.) and cover an entire cake with it. Why reserve the shell border just for the border? It’s time to make a rainbow!
First, my elaborate sketch. I included this just for fun ;0) – I always smile when I see the gorgeous sketches that people post online of their cake plan. I smile because I know that my sketches, when I make one at all, normally look like this— (this is what I drew for Mom when she was asking what I had in mind) ! We decided to go with half a rainbow. As you’ll see in a second, maybe I should have gone all out and used some colored pencils -haha ;0) hmmmm….see Red Alert! below…
The cake that I’m using today is a tall 6″ tier. I’ve been doing a lot of these lately. Mine is two cake layers, then a small cake board in the center (doweled beneath) with another two layers stacked on top and frosted as one. I frosted my cake with a thin layer of frosting…we will pipe over this in a few minutes.
You can see that I used a paintbrush handle to map out where my rainbow would fall.
The most time consuming part of this or any rainbow cake is tinting the frosting! I used Americolor coloring gels to tint my frosting but go with whatever your favorite may be.
Red Alert, Warning!!
Okay, so here’s the part where I dive into the piping. I’m using a Wilton 21 star tip (use whatever medium sized star tip you’d like).
As I’m thinking to myself, Red- Orange-Yellow-Green-Blue-Violet…., I SHOULD have been thinking…Violet-Blue-Green-Yellow-Orange-Red. I made this cake yesterday, and it wasn’t until TODAY that I realized I’m completely backwards!! I think the half-rainbow threw me off…and the fact that I was working from left to right, and I may as well assume that what I really needed was another cup of coffee ;0)
Here we are, three rows in! Yes, a little backwards, but still pretty!
Our half rainbow is now complete! Now, I’m piping shells (still with the Tip 21) to fill in our sky. My blue is Americolor Sky Blue.
You can see in the picture that I’m slightly staggering my shells, so that each row can be nestled into the row below it. It’s optional–if you pipe each row exactly as the row before it, you’ll have more openings to your crumb coat beneath.
More shells….
More and more and more shells ;0)
Have I mentioned that I love piping shells?
Now…let’s have some clouds! Things are about to get very PUFFY! If you aren’t into puffy, then a nice smooth top, or a “shell top” would be great too.
I’m armed with my Ateco 806 tip, which is a jumbo round tip. I also used my Wilton 12 tip, which is a medium round (and with enough pressure, is almost identical to the 806).
Wahoo! Hooray for clouds ;0) — I tapped down all of those points once my icing had crusted a little.
Now for some gold. Use whatever you’d like for this…I used jumbo gold dragees that I break out for special occasions like these. They aren’t meant to be eaten, but they are pretty! Gold chocolate coins, or fondant painted with gold luster are other ideas ;0)
Also, I opted to throw out the pot of gold (which was in my sketch, did you notice?) — I didn’t want to bring in the color black. Plus, I figured that most people would be just as happy to find a pile of gold at the end of the rainbow. I know I would!
And we are finished–hooray! I hope that you enjoyed this tutorial– Even if for no other reason than to consider the “shells all over” look. If you try out this rainbow cake, I’d love to see! Maybe your colors will be in the right order, but if not, it will still be lovable ;0)
Close up! I could have piped buttercream puffy clouds all day! ;0)
Need a great classic vanilla buttercream recipe? We have just the one!: Classic Vanilla Buttercream
If you’re interested in even more cheerful rainbow cake fun, we have a roundup of the BEST rainbow cake recipes, tutorials, and inspiration! Follow the link to check it out!: Roundup of Rainbow Cakes!
Thanks for stopping by! We hope that you enjoyed this rainbow cake cuteness! If you give it a try, make sure to leave a photo in the comments below. We would love to see your work!
It looks perfect just the way it is. By the way, which way should it be, I can’t figure that out lol.
Thanks Muazza!! Usually moving from top to bottom, a rainbow would be red, orange, yellow, green, blue, violet–my rainbow is curving the wrong way for the color pattern that I did. Most people probably wouldn’t have noticed though ;0)!
This is good practice for piping shells!
Thank you so much for this lesson! I had promised my daughter a my little pony cake and knew I wanted to do a rainbow because rainbow dash is her favourite :) this was perfect!! I was rushed for time so it didn’t come out quite as clean as I had wanted but the kids LOVED it! I also did the cake itself a rainbow tie-dye so that was a fun surprise when we cut it <3
Carly, I’m so happy to hear that you made this! Your design sounds perfect–I love the idea of the rainbow tie dye on the inside too! ;0)
Beautiful cake! I love the bright colors against the sky blue background. Thanks for sharing! : )
Hi Mellisa I want to ask you what is the frosting on the cake- Italian merengue cream or just whipping cream? Thank you!
Hi DiDi, Melissa used her Fluffy Buttercream recipe from the Recipe Section, here is a link,https://www.mycakeschool.com/recipes/fluffy-vanilla-buttercream/
How do you get the red so red? I use Americolor super red and mine is never a true red.
Hi Casie, We use Americolor super red also, we don’t do anything special. Ours is not a true red either, but red enough.
Would you mind sharing the gel color used for the blue sky?
Thank you
Hi Jenny, Melissa used AmeriColor Sky Blue. If you need the other color names, she list them on the 6th comment under the last picture.
I LOVE THIS!!! I may even just put marshmallows on top. My kids love marshmallows :)
Thanks Amy! Love that idea!
How much icing should I make??? Thanks! So cute, I love it!!!!
Hi Elena, I think you should double the buttercream recipe. There are so many colors, plus white for the fluffy clouds, I think you should double the Classic Vanilla Buttercream recipe. If you have any leftover, it can be frozen in an airtight container for 3 months to use on another baking project.
Thanks so much, I eventually saw deep in the comments that it was doubled. It turned out great : ) My new favorite icing recipe for sure!
Hi Elena, Thanks for your follow up, I’m happy it turned out great!