Rainbow Unicorn Birthday Cake

My youngest baby turned 6 years old on Saturday. I keep calling them babies. My husband keeps telling me the girls aren’t babies anymore, but they will always be my babies.

Unicorn Birthday Party

After a bad experience with a purchased birthday cake, I started making birthday cakes for my girls and it has turned into a tradition. I feel like the cakes get bigger and better every time. I recently did a Minecraft cake for my oldest daughter’s birthday party.

Haleys Birthday Unicorn Invite FINAL IMG

Haley loves all things unicorn so I decided to do this unicorn themed cake I’ve seen circling around the internet lately. It turned out amazing, but it was harder than I had expected.

I’ve done stacked cakes with fondant in the past, but this was my first time making the rainbow colored cake inside. And I’ve never had to stack 6 layers before!

Unicorn Rainbow Cake Birthday Party

I used two french vanilla cake mixes, and split each cake into thirds, so I ended up with 6 thin layers. Each layer was about 2 cups of cake batter and only took about 10 minutes to fully bake.

Unicorn Birthday Party

After they cooled down, I stacked the cakes with buttercream frosting and stored the cake in the freezer overnight.

Unicorn Birthday Party

I originally planned to skip the fondant and do smooth buttercream for the unicorn face, but I couldn’t get my frosting perfectly smooth like I wanted it, so I covered my cake with homemade marshmallow fondant.

Unicorn Rainbow Cake back

The unicorn horn, ears, and eyes are made of marshmallow fondant. I used edible gold dust (Wilton Pearl Dust, gold) mixed with lemon extract to paint the gold on. I painted the gold mixture on three separate times to get a deeper gold color.

Rainbow Cake

If you are making this cake and don’t have a lot of practice, I would skip the rainbow inside and just focus on perfecting the outside. This cake took me 2 full days to complete so start early and plan accordingly.


The cake was a huge hit at the party, and Haley had a great time celebrating with her friends! If you enjoyed this post, please share this post and Follow Me on Pinterest! And let me know if you make a Rainbow Unicorn Cake of your own!