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How to Make a Rainbow Unicorn Cake

How to Make a Rainbow Unicorn Cake

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Step-by-Step Instructions on how to make the popular (and delicious) Rainbow Unicorn Cake the next time you have a birthday party!

The unicorn trend is super hot right now and it’s clear to see why. We all could use a little bit of the happy, magical vibe these mythical creatures give off! I am seeing this popular cake all over my Instagram feed.

This rainbow unicorn birthday cake is just what every little (or big) kid will be delighted to see at their unicorn birthday party! I’m sharing step-by-step instructions on how to make your own rainbow unicorn cake! 

I just love to bake cakes and I have been making my kids’ birthday cakes for years now. I started with simple box cake mixes and now have worked up to making my own homemade cakes and frostings

rainbow unicorn cake

What I love about this Unicorn Cake is that it looks just like you picked it up from a bakery, except you didn’t. You made it! While this fun sweet treat for your themed party looks like it was a lot of work, I am positive you will have a great time creating the rainbow effect and unicorn mane.

The easy rainbow unicorn cake is made of a simple vanilla cake dyed beautiful hues of green, pink and blue with food coloring to make the rainbow layers. The whole cake is iced with my favorite vanilla buttercream frosting and then decorated to resemble a unicorn. 

While I chose to use these colors, you can certainly choose any color combination you’d like or that fits with all types of special occasions. I have also changed the primary color of the white frosting to be a pretty pale pink and a lavender color. They also sell edible gold paint if you want to give your frosting a pretty glimmer of gold.

rainbow unicorn cake

How to make a Rainbow Unicorn Cake

I have a video tutorial below for you to see how to make this beautiful cake hands on. You can find most of these items at grocery stores or amazon. I have provided an affiliate link for you to make your shopping easier.

Equipment:

Ingredients

  • 2 White Boxed cake mix, prepared according to box instructions, colored and baked.
  • Buttercream icing

Before you make your cake, I highly suggest you read my baking basics guide and my guide to cake decorating.

rainbow unicorn cake

Bake Your Rainbow Unicorn Cake

Prepare cake mix according to the box’s recipe instructions in a large bowl. Separate the cake mix into four different bowls using the electric gel food colouring to make each a different color. 1 to 2 drops of coloring will be enough for a bright rainbow cake color.

Lightly grease 8-inch cake pans and line the bottom of the pans with parchment paper. Pour the cake batter into your prepared pans.

Bake according to box instructions. Because these are 1 inch cake layers, which are different sizes then what the box says, they may cook faster. Begin to check them at the 15 minute mark. Cakes are done when you stick in a toothpick in it and it comes out clean.

Remove from oven and allow to cool at room temperature until the cakes can be wrapped in plastic wrap in the freezer. While freezing the cakes is not necessary it is strongly encouraged as it will make the icing of the cake easier when it’s time to assemble. If you are in a rush chill the cakes in the fridge for at least two hours before attempting to assemble the cakes or else the cakes can come apart when you are icing them.

Make your buttercream

Crumb coat the cake with a thin layer of vanilla buttercream, making sure to put a small amount of buttercream in between each of the layers of cake.

Allow the cake time to rest before moving on to the next step. The buttercream icing will crust over meaning when you touch it with your finger after about 15 minutes the Icing is no longer wet.

Prepare your colored frosting and put into piping bags with star tips. While using a color is not necessary for this particular activity it will be helpful to change the tips out.

Assemble the Unicorn

Remove the unicorn horn cake topper from its package and center at the top of the cake, along with the unicorn ears.

rainbow unicorn cake

After placing the unicorn horn topper on top of the cake select your black eyes and place them on the front of the cake, as symmetrical as possible. The easiest way to do this may be with a pair of tweezers.

A medium stiff consistency icing and a star tip is going to be required to create the roses on the top layer of the cake, which will be the unicorn’s mane.

rainbow unicorn cake
rainbow unicorn cake

How to Store Your Unicorn Cake

Store your cake in the refrigerator until you are ready to display your beautiful rainbow unicorn cake on a cake stand. You may need to adjust your refrigerator’s shelves to help the cake fit.

If you want to make your cake layers in advance you can! After they completely cool, wrap each cake layer in plastic wrap and then aluminum foil. You can freeze your unicorn cake layers for up to 3 months. When you are ready to thaw out your layers, start out in the refrigerator overnight and then let them come up to room temperature.

Common Questions About Making a Rainbow Unicorn Cake

What do I do if I don’t have a piping bag?

While I strongly encourage you to purchase piping bags, you may use a small sandwich bag but it will require you to have a piping tip.

Can I use plastic tips?

Yes you can use the plastic decorating tips. However you will not be able to change out the tips while you’re decorating.

rainbow unicorn cake

Why do we use couplers when decorating?

The couplers make it easy for you to change the piping tip while still using the same color.

What’s the best way to clean the piping tips?

Boil them in hot water and allow them to air dry.

Best practices when frosting:

Make sure you hold your piping bag at a 45° angle. Apply even pressure when squeezing out the icing. Stop squeezing and then pull your tip away.

rainbow unicorn cake

If you are looking for more unicorn inspiration, check out my unicorn cupcakes or unicorn donuts!

More Unicorn Party ideas:

cake decorating
rainbow unicorn cake

How to Make a Rainbow Unicorn Cake

Yield: 1 cake
Prep Time: 10 minutes
Cook Time: 15 minutes
Additional Time: 2 hours 30 minutes
Total Time: 2 hours 55 minutes

Step-by-Step Instructions on how to make the popular (and delicious) Rainbow Unicorn Cake the next time you have a birthday party!

Ingredients

  • 2 White Boxed cake mix
  • Buttercream icing
  • Unicorn sprinkles mix
  • Unicorn cake topper
  • Electric Gel Colors

Instructions

    1. Prepare cake mix according to box instructions.
    2. Separate the cake mix into four bowls using electric gel colors 1 to 2 drops of coloring will be enough for a favorite cake color.
    3. Lightly grease cake pans and line bottom of the pan with parchment paper.
    4. Pour batter into pans and bake according to box instructions.
    5. Because these are 1 inch cake layers they may cook faster than your box tells you. Begin to check them at the 15 minute mark.
    6. Cakes are done when you stick in a toothpick in it and it comes out clean.
    7. Remove from oven and allow to cool at room temperature until the cakes can be wrapped in plastic wrap in the freezer.
    8. Make your buttercream.
    9. Crumb coat the cake with a thin layer of vanilla buttercream making sure to put the buttercream in between each layer as you build a cake.
    10. Allow the cake time to rest before moving on to the next step. The buttercream will crust over, meaning when you touch it with your finger after about 15 minutes the Icing is no longer wet.
    11. Prepare your colored frosting and put into piping bags with star tips. While using a color is not necessary for this particular activity it will be helpful to change the tips out.
    12. Remove the unicorn horn cake topper and the ears from its package and center at the top of the cake.
    13. After placing the unicorn horn topper on top of the cake select your eyelashes and placing them as symmetrical as possible.
    14. A medium stiff consistency icing is going to be required to create the roses on top of the unicorns head using a star tip we will be able to create roses on top of the cake.

Did you make this recipe?

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