This is an easy version of a decorated cake suitable for any level baker. You just need some buttercream and a few decorating tips and you are on your way to a masterpiece!

Create a beautiful, show-stopping cake with only open star tips!
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Rainbow Cake

The hardest part (which is not even hard, just time consuming) is preparing the frosting. And that can be done well in advance!

To make this cake you will need:

Cake to decorate (I adore this Perfect White Cake recipe)

Buttercream recipe (below)

Food coloring – I used McCormick

Decorator’s tips: 16, 18, 22, 172, 195, 9FT (this is simply a wide variety of the same style of tip- see how to store all of these tips HERE)

Create a beautiful, show-stopping cake with only open star tips!

Disposable pastry bags and coupler sets (3 regular couple sets for the 16, 18, 22 tips)

Rotating cake stand (my favorite is the Fat Daddio stand shown at the end of this Cake Stand 101 post)

Create a beautiful, show-stopping cake with only open star tips!

Here is the buttercream recipe that I find works the best with piping:

Recipe from Decorator’s Buttercream.

Create a beautiful, show-stopping cake with only open star tips!

Here is a quick video showing just how easy this technique is!

Tips for Success:

Bake cake, cover in crumb coat, (here is a video of me adding a crumb coat) then go back and do your final “beauty” layer. Try and get the frosting as smooth as possible! I found that the contrast of the crisp, clean lines of the cake with the whimsical multi-colored buttercream “stars” is really quite impressive.

When you have added color to your frosting, immediately add it to your pastry bag. The frosting can actually be stored right in the bag! When you are ready to decorate your cake, prepare a NEW, empty bag with a coupler set. Cut off the tip of the bag that has the frosting and simply drop it into the empty bag with coupler set. If you were to run out of frosting, simply remove the empty bag from the bag with the coupler set and replace with a new bag of frosting. This is such an easy way to use frosting and often means less mess and clean up for you!

You can use as little as 3 different decorating tips as well as add other varieties and styles! For instance, you could add some round tips in for detail or a leaf tip for extra added fun.

Create a beautiful, show-stopping cake with only open star tips!

Anyone can try (and master!) this technique. Most of the tips and tools are available online and major retailers.

See my Mother’s Day version of this cake HERE!

Create a beautiful, show-stopping cake with only open star tips!

Decorator’s Buttercream

Prep Time 20 minutes
Total Time 20 minutes
This is easy version of those stunning (and sometimes labor intensive) cakes!


  • 1 cup (2 sticks or 227g) unsalted butter, room temperature
  • 1/2 cup (115g) shortening
  • 2 tsp. fresh lemon juice (or 1 tsp lemon extract)
  • 6 cups (just over a pound) confectioners’ sugar
  • 1/4 cup 60g whole milk*
  • 2 tsp. meringue powder**
  • 1/2 tsp. table salt


  • In a stand mixer with the paddle attachment, cream shortening and butter on medium-high until fully combined and fluffy, about 3 minutes.
  • With mixer on low speed, add lemon juice (or extracts) and salt.
  • Slowly add sugar, one cup at a time. Add meringue powder. (The mixture will appear dry.)
  • Add in milk. Turn the mixer up to medium-high (or high) and beat until light and fluffy (approximately 5 to 8 minutes).
  • *You may need to add more milk to reach your desired consistency. Start with the 1/4 cup and if the
  • buttercream is still too dry, add in more milk 1 tablespoon at a time until you reach the desired consistency. Make sure the mixer is on low speed when adding in milk and give it at least 30 seconds between each addition.
  • **You can omit meringue power if you prefer. To achieve the perfect piping consistency, you may need to add more confectioner’s sugar.


  • For extra smooth frosting with less air pockets, add buttercream to a food processor 1/2 batch at a time.
  • Process for 3-5 minutes on high, or until frosting appears smooth and creamy like ice cream.
  • Place directly into piping bags and seal with a rubber band. Can be stored in piping bag until ready to use, up to 3 months.

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Create a beautiful, show-stopping cake with only open star tips!
Create a beautiful, show-stopping cake with only open star tips!

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Meet Amanda Rettke

Amanda Rettke is the creator of I Am Baker, and the bestselling author of Surprise Inside Cakes: Amazing Cakes for Every Occasion – With a Little Something Extra Inside.Over the course of her 15+ year blogging adventure, she has been featured in and collaborated with the Food Network, New York Times, LA Times, Country Living Magazine, People Magazine, Epicurious, Brides, Romantic Homes, life:beautiful, Publishers Weekly, The Daily Mail, Star Tribune, The Globe and Mail, DailyCandy, YumSugar, The Knot, The Kitchn, and Parade, to name a few.

Reader Comments

  1. Absolutely beautiful. I made this for my best friends birthday and she was so impressed. Who am I kidding, I was impressed with me too. I’ve never done icing work like this. Thank you for posting this great design. I love your site, I’m learning so much from you and gaining confidence in my abilities.

  2. Does the frosting recipe make enough to frost the cake and put between the layers, AND create the star decor? Thanks!

  3. If you want to make it a true 7-color rainbow how would you make Indigo?
    I guess another way to ask is do you mix food colorings to make the colors you want? I think McCormick only has 4 colors to choose from, correct?

  4. Beautiful!! But how do you make your Icing colors so bold and bright? I would appreciate the tip. Thank You!

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