Introduction: Rainbow Buttercream Layer Cake

My son loves color. So naturally for his birthday he requested a cake in his favorite color- RAINBOW! I am not a cake baker but was pleasantly surprised how easy and amazing the rainbow effect turned out. He was over the moon for his birthday cake and it was truly delicious.


3 cups unsalted butter (room temperature)
11 cups powder sugar
1/3 cup heavy whipping cream
1 1/2 tablespoon pure vanilla extract
1 teaspoon salt
Gel food colorings

Stand mixer (or hand mixer)
Bench scraper
Piping bags with ties
Wilton #2D drop flower tip (optional)
Cake stand (preferably one that spins for easier decorating)

Step 1: Bake a Cake

You can use any cake recipe to make a layer cake. Even a boxed cake mix will work. My cake is 3 layers baked in 7 inch cake pans. While your cake is cooling you can start making the buttercream.

Step 2: Measure Out Ingredients

It is always easier to bake or make any recipe when you pre measure your ingredients and they are on hand and ready when you need them.

Step 3: Cream the Butter

Add 3 cups of room temperature butter to your stand mixer and cream for about 1 minute. This will make your buttercream fluffy and creamy. Once you cream the butter be sure to scrape the sides down with a spatula.

Step 4: Salt + Vanilla

With your mixer on low, add in your salt and vanilla until it is just combined. Scrape down sides once more.

Step 5: Powder Sugar + Whipping Cream

With your mixer on the lowest speed, add in your powder sugar one cup at a time. After about 3 cups drizzle in some heavy whipping cream to keep the frosting smooth. Repeat this pattern until all of sugar and cream is incorporated.

Step 6: Whip the Buttercream

After all of your ingredients are added whip the buttercream on medium speed for about 2 minutes to fluff it up.

Step 7: Layer Your Cake

Stack your cake layers with a thin layer of buttercream in between. Add a crumb coat and pop it in the fridge to firm up. A crumb coat is simply a thin coat of frosting covering your cake so it’s easier to decorate after chilling in the fridge.

Step 8: Piping Bags + Gel Food Coloring

Choose your colors and have your piping bags ready to add each color to.

Step 9: Create Your Colors!

Using about a cup of frosting per color, mix the gel color in. I use one bowl and rinse it between each color to save on dishes. Once I achieve my desired shade I scrape each color into a piping bag and tie it up. I wait to cut the tips off to prevent mess and hardening of the buttercream in the bag.

Step 10: Wilton Tip on White Frosting Bag

For some added decoration, I add leftover white frosting in a piping bag with my Wilton tip (mentioned above). This is optional but who doesn’t love some extra decoration!

Step 11: Cut the Tips Off the Colored Piping Bags

Once your cake has chilled and is ready to be frosted, cut the tips of the piping bags off each color. Try and cut the same amount off of each bag for equal thickness when piping.

Step 12: Pipe Your Frosting in Layer Up Your Cake

Starting at the bottom begin to pipe your colors in stripes around the cake up to the top. This is when a rotating cake stand comes in handy. It makes the piping process a breeze!

Step 13: Smooth Those Stripes!

Using your bench scraper, start smoothing the buttercream around the cake. I have the most success with this if I hold my bench scraper still and rotate my cake stand to smooth. It keeps my hand steady so I stay in the color lanes. Repeat this process on the top of the cake if you desire!

Step 14: Add Some White Buttercream Decorations

Using the extra white buttercream that was set aside with the Wilton tip, get creative! I chose to decorate the top of my cake with what I call “ice cream swirls” feel free to make it your own and add as much or as little decoration as you want.

Step 15: Rainbow Swirl!

If you have any colored buttercream left make a rainbow swirl! Grab a piece of plastic wrap and lay it flat on the counter. Pipe a stripe of each color next to each other then fold over on top of each other and roll it up into a tube. Cut the tip of the plastic wrap off and drop down into a clean piping bag with the Wilton tip attached. Once you squeeze the bag the colors will all swirl together! This is also a fun cupcake idea instead of making a cake.

Step 16: Pipe the Rainbow!

Have fun decorating with this rainbow swirl! Again this is totally optional but I love the way it came out!

Step 17: ENJOY!

You are done! Enjoy your creation!

Colors of the Rainbow Contest

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Colors of the Rainbow Contest