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DIY Rainbow Cake (for Beginners)

When you ask your opinionated almost 4 year old what she'd like for her birthday and she responds with a "Unicorn, rainbow, Fancy Nancy, Spa Day Birthday", you know you're in trouble... After I took a day to wrap my head around what that could possibly entail, the ideas started brewing....

From a unicorn tent to arts and crafts, a few games, yummy treats, and a girls' spa day fit for a unicorn princess dressed to the nines in her Unicorn Party Dress ensemble, these girls were in for a treat!

Before we get started with the cake though, I couldn't resist posting just a few of the birthday photos....

Check out the blog post, Unicorn Spa Day Birthday Bash for more fun ideas, decor inspiration, games, arts and crafts, food ideas, and more!


To go along with the unicorn and rainbow theme, my daughter "naturally" requested a rainbow unicorn cake so that part was fairly easy. I asked around on a few Mom's groups and found an amazing cake artist that made the top part of the cake (the unicorn cake) for only $35! If you know your way a little around the kitchen and also have the time, you could also create this on your own with this Unicorn Cake Topper kit.

Due to minimal time and 2 little toddlers, I opted for a cake decorator to make the top part though. This icing on the cake (pun intended) was that it included 6 rainbow layers! Done and done! My girl was thrilled!

Then of course I happened to come across this awesome cake recipe with a rainbow inside, and since I've never made a cake from scratch and love a good challenge, I got the itch to try it.

I followed the steps as best as I could with a toddler helping... Here is the modified recipe from Emma's Goodies.

INGREDIENTS for the Rainbow Cake (3) 9" pans:

- 2 sticks of Butter

- 6 Tbsp Coconut Oil (can use other oils too) (=1/4 cup plus 2 T)

- 1 1/2 cups Sugar

- 1/4 cup Vanilla Extract (use baking vanilla to avoid brown vanilla)

- 6 Eggs

- 3 1/2 cups Flour

- 2 Tablespoons Baking Powder

- 1 tsp Salt

- 1 cup unsweetened full fat Yogurt

- 1/2 cup Milk (regular milk)

- Gel Food Coloring (I love this brand!)


1. Preheat oven to 350°F.

2. Take butter out to soften butter.

3. Measure and combine dry ingredients (flour, baking powder, salt).

4. Lightly butter and flour the pans. Cut 3 parchment paper circles to line pans and place a circle in each pan. You can lightly rebutter and flour parchment circles or leave as is depending on preference.

5. In a separate mixing bowl, combine and cream the softened butter with the following: coconut oil, sugar, and vanilla.

6. Add eggs one at a time. Don't over beat the eggs or the air will crack the top of the cake.

7. Add the other liquid ingredients: milk and yogurt.

8. Add dry ingredients (flour, salt, baking powder) and mix together. Some people sift the dry ingredients to eliminate lumps. I did not. Mine turned out fine. I'm not aiming for perfection here, nor have the time.

9. Separate the dough into 6 bowls and use Gel Food Coloring to color each bowl of cake batter with a different color of the rainbow (I also used pink so I made 7 bowls. The pink and red kind of blended together though so I didn't find the pink to be necessary). If you plan on doing all 3 cakes in standard rainbow order (Red, orange, yellow, green, blue, purple), then you'll need more red, orange, and yellow (decreasing how much you use with each next color used) since you'll use more at the beginning to cover more of the pan compared to the last color. See the tip below on the "Inverted Rainbow" for another option too. Mix each batter well with a spoon.

10. Read this step completely before you start adding the colors. Start with the red cake batter and place a few big spoonfuls into the cake pan. Tap the pan onto the counter to help level it out. Have an idea how much you'll use of each color to map it out so you don't waste any cake batter (you'll use more for the beginning colors like red, orange, yellow, since they will take up more room). Continue adding colors of the rainbow (orange, yellow, green, blue, purple) into the center of the pan and gently tapping the cake pan onto the counter after each color is added to level the cake out. You can do this for all 3 cake pans or do this for 2 cake pans and make an inverted rainbow for the middle cake layer (see "TIPS" below). I ended up making one cake with the standard rainbow order (starting with red as the base/on the bottom) and 2 cakes with the inverted order (starting with purple as the base). You'll want to make sure all the cakes are the same size, so you'll have to plan ahead a little as the first color (ex. red) will have a lot more than the last color (ex. purple) for the standard rainbow order.

11. Bake for 25-30 minutes until toothpick comes out clean.

12. Let cakes cool for 5 minutes in pan, then turn them over and take them out of pan to cool completely. Let cakes cool completely before you place them in fridge. This picture above shows the standard rainbow pattern for 1 cake and the inverse rainbow pattern for 2 cakes.

13. After cakes are cooled completely, wrap each layer individually in Saran Wrap and place them all in the fridge.

We'll get to the frosting part soon, but a few more tips and lessons learned first!


  • If you want the colors to be more vibrant, use Clear Vanilla Extract instead of pure vanilla. The pure vanilla has a brown coloring which will make the colors a little darker, but it really wasn't that noticeable if you prefer the pure vanilla. I used pure vanilla for the first batch above and extract in the second batch (below).

  • I love the Ann Clark brand for the Gel Food Coloring as the colors are very vibrant, a little goes a long ways, and they blend well. I can't wait to try them for making macarons this fall!

  • You can make an inverted rainbow as well by reversing the colors of the rainbow. You can use the inverse for the middle rainbow layer. So place a few big spoonfuls of purple in the pan, followed by blue, green, yellow, orange, and red. This does look kind of cool when the middle layer is inverted, but having all 3 layers the same works too!


Let's just say when you have your toddlers helping you make a new recipe, be prepared for a few blunders... The rainbow colors turned out amazing....

Then the timer went off... and after squinting at the cake trying to make sure my eyes were working correctly, I realized something was off, very off... The cake did not rise! It was about 1/2" thick and had lots of holes kind of like a sponge cake!

After careful speculation and review of the recipe with my mama, we realized I forgot a cup of flour (I doubled the recipe and clearly my math skills were not up to par that night) and the baking soda was never added.....

I couldn't just throw it all out, so I got creative and decided I would figure out a purpose for these cakes...

I'd like to introduce to you, "Rainbow Pudding Cups"... They didn't particularly taste great (at least IMHO), but my daughter loved them, and I guess that's all that mattered!

Back to the drawing board, or kitchen island in this case.

The second attempt was much better... though I got to the very end of the layers, and running on 4 hours of sleep for the 7th day in a row (hello 2 toddlers who take turns wanting to party in the middle of the night), my butter fingers dropped the bowl into the inverted rainbow pan.... So transforming the inverted rainbow cake into a forced psychedelic cake was the next step.

Of course my daughter said that cake was her favorite.... if the birthday girl's happy, I'm happy!! I used the psychedelic cake for the middle cake layer. The mistake actually turned out to work out just fine, but you can imagine what it would look like if the middle cake layer ended up being the inverted rainbow after all.

This method was super easy and I'll definitely be trying it again!


Before we get into frosting the cake, a few things you'll need are a Cake Board Circle and Cake Decorating Set. I'll go into that more soon.

For a quick frosting and sprinkling tutorial, first you let the cake cool completely. Then you wrap each layer individually in Saran Wrap and place it in the fridge which will help the frosting adhere to the cake. I let the cake chill overnight in the fridge.

For an easy and delicious cream cheese frosting recipe, I modified the recipe below from Emma's Goodies.


  • 24 ounces cold Philadelphia Cream Cheese

  • 1 stick of Softened Butter

  • 2 1/2 cups Powdered Sugar

  • 2 Tbsp Vanilla Extract


  1. In a mixing bowl, combine vanilla and cold cream cheese together. Combine together with a mixer.

  2. Slowly add powdered sugar (one spoonful at a time), using the mixer to combine.

  3. Add softened butter and mix well.


  • Before you apply the frosting, make sure your cake tops are fairly level and even. If a cake is made properly, it normally will be fine the way it is. If there is a tall round dome on your cake top, it helps to use a serrated knife to gently shave the dome off to flatten the cake a little. I didn't have to do this for these cakes, but have done this trick before if the cake is very uneven (top middle part is much higher). If the cakes are fairly level, frosting the cake and the layers will be much easier.

Next you'll apply a thin crumb coat of the frosting to the cake (inbetween each of the cake layers, to the sides of the cake, and to the top of the cake). I did this the night before the party. This helps to "glue" the crumbs down and helps to avoid stray crumbs and cake pieces from breaking off the cake when decorating the cake. It also helps to seal in the moisture and provides a smooth finish for the final frosting.

After I completed the crumb coat and let it sit overnight, the next day I frosted the cake with the remaining frosting. Having the right tools like an icing spatula, icing smoother, and turntable is key for this! If you don't have these items at home, this basic Cake Decorating Set is a decent price and well worth the investment too! This was my saving grace and why I was able to frost the cake so quickly!

I used the icing spatula to slather the frosting on and get a semi smooth surface. Then as I turned the cake with the turn table, I held the icing smoother and let the turn table do the work. I wiped the smoother off as needed. I then used the icing smoother to finish smoothing the sides and top of the cake for a smooth, polished finish.


After researching a few methods of applying sprinkles all over the cake, I landed on the approach that was the easiest and quickest, which worked out to my favor since I literally frosted and sprinkled the cake at 2:25pm when guests arrived at 2:30pm...

After frosting the sides and top of the cake, I then placed the cake (still on the turn table) into a large plastic tote before the frosting had set. You'll want to do the sprinkles quickly before the frosting sets. Use gloves for sanitary reasons and gather a handful of sprinkles and gently stick the sprinkles to the sides of the cake to cover the cake in sprinkles. Then sprinkle the top of the cake with sprinkles. Patch up the bald spots as needed.

Clean up the edges of the cake with a pallet knife by cleaning up the excess sprinkles on the cake board. You can also push the extra straggler sprinkles into the cake base to make a nice smooth finish to make the cake board look nice and tidy.


  • You won't want to sprinkle your cake too far in advance as the colors of the sprinkles can start to bleed into the frosting. A good rule of thumb is to sprinkle the cake a few hours before the event (or up to 12 hours before the event).

Again, I am not a professional cake decorator, just a DIY-er, but I've used straws to stack 2 cakes a few times now and so far I have a good track record. You can use other straws, but I saw this tip on a baking show and love these Boba Straws. I won't go into the details here as this post has already gotten pretty long, but I'll save that for another day.

Happy baking and thanks again for reading! Check out the post, Unicorn Spa Day Birthday Bash for even more fun unicorn and spa day birthday party ideas!


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This lifestyle blog is a sampling of my many passions and interests that are a reflection of my soul essence.
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