Learn how to make a fun Rainbow Cake that actually looks like a rainbow with this doable method anyone can do—even novice bakers! This method is a super fun way to make a kids birthday cake to delight the kids…especially the rainbow-lovers.
Rainbow Cake
My middle kiddo has loved rainbows for as long as I can remember, and for her fifth birthday, requested a Rainbow Cake. And after looking online and finding a lot of cakes with rainbow layers, but none that actually looked like a rainbow—which is what she wanted—we came up with this easy method.
To make this cake, you simply bake a round cake, and cut it in half. Then you use frosting to sandwich the halves to make your rainbow cake. Best of all? The cake is so fun that it doesn’t even matter if the rainbow colors look perfect…or anything but!
This is (for sure) one of my most elaborate recipes, but while there are a bunch of steps, nothing is hard. And the pay off at the end is so worth it!
Ingredients You Need
To make this cake (and the frosting) you’ll need:
- Unsalted butter: This allows us to add just a little salt to round out the flavors.
- Sugar: I use granulated sugar in this cake recipe.
- Eggs
- Vanilla extract
- Whole milk: Have this at room temperature if possible.
- All-purpose flour: This flour helps the cake stay light and fluffy.
- Baking powder
- Salt
- Sprinkles: I like to add nonpareil-style sprinkles to the cake to make it have pops of color!
TIP: Then for the frosting and decorating, you’ll need cCream cheese, powdered sugar, ffood coloring, and marshmallows.
Step-by-Step Instructions
Here’s a look at what you’ll need to do to make this cake.
- Beat the butter and sugar with a hand-held electric mixer.
- Add in the eggs and beat to combine.
- Add in the milk, flour, and other dry ingredients and mix gently to combine.
- Gently fold in the sprinkles. Add batter to pan.
- Bake.
- Let cool fully.
TIP: I usually make the cake the day before I plan to serve this to cut down on how much work I need to do on any one day.
How to Assemble the Cake
Once you have the cake made, you’ll need to make the frosting and put the cake together. Here’s how. Scroll down to the bottom of the post for the full info.
- Beat the frosting together.
- Divide into bowls.
- Add food coloring.
- Carefully cut the cake in half.
- Use one color (I used red) to stick the two halves together, then cover the top.
- Add the remaining colors, one at a time. Cut the marshmallows in half and add to the bottom of the front and sides.
TIP: This does not have to be perfect. It’s so fun regardless!
Frequently Asked Questions
Sure! Just choose a few colors. That would be an easy way to make this easier.
I used a small cake icing spatula. I find the smallest size to be easiest to manage. A small butter knife could work too.
Sure, you can use whichever type you prefer. I like the ones from India Tree.
How to Store
- This cake is best on the day it’s assembled Cover any leftovers with plastic wrap and store at room temperature for up to 2 days or in the fridge for 3-5.
- You can bake the cake the day before you plan to serve it. Let it cool fully on the wire rack, then place onto a plate lined with parchment paper and cover tightly with plastic wrap to make sure it stays fresh. (Or line a large airtight container with parchment paper and cover.) Store at room temperature.
Best Tips for Success
- I used gel food coloring from Wilton for bright colors. Any will work. (This is a natural option from India Tree.)
- I like these plant-based food coloring options.
- I like to add nonpareil-style sprinkles to the cake for a pop of color in each slice.
- A small cake icing spatula is a good tool for adding the frosting, though a butter knife can also work.
- Place candles on top for a birthday cake.
- You may have a little of each frosting color left over.
- Make the cake chocolate using my Healthy Chocolate Cake recipe.
Related Recipes
I’d love to hear your feedback if you try this recipe, so please comment below!
Favorite Rainbow Cake (for Kids Birthdays)
Ingredients
Cake
- ½ cup unsalted butter (1 stick, softened at room temperature)
- ½ cup sugar
- 2 large eggs (at room temperature if possible)
- 2 teaspoons vanilla extract
- ½ cup whole milk (at room temperature if possible)
- 1 ¼ cups all-purpose flour
- 1 ¼ teaspoon baking powder
- ¼ teaspoon salt
- 1 tablespoons nonpariel style sprinkles (optional)
Frosting
- 1 cup unsalted butter (2 sticks, softened at room temperature)
- 12 ounces cream cheese (softened at room temperature; 1 ½ standard size packages)
- 1/2-1 cup powdered sugar
- 1 teaspoon vanilla extract
- 5 colors food coloring
- 12-16 regular size marshmallows
Instructions
To make the cake:
- Preheat the oven to 350 degrees F and grease a 9-inch round cake pan with nonstick spray very well. (I use Classic Pam.)
- Add the butter and sugar to a medium bowl. Beat with a hand-held electric mixer on medium-high speed until light, fluffy, and thick or about 3-5 minutes.
- Add in the eggs one at a time, beating in between to fully incorporate each egg.
- Add in the vanilla.
- Add the baking powder, salt, and half of the flour to the bowl. Beat on the lowest speed. Add half of the milk. Beat on the lowest speed. Add the remaining flour and milk and beat on the lowest speed to just combine the batter. Gently fold in the sprinkles if using.
- Add the batter to the prepared cake pan.
- Bake for 24-26 minutes or until just golden brown around the edges and a cake tester inserted into the center comes out clean.
- Remove from the oven. Run a knife around the edges, and invert carefully onto a wire rack to cool completely.
To make the frosting:
- Add the butter, cream cheese, ½ cup powdered sugar, and vanilla to a large bowl. Beat with a hand-held electric mixer, starting on slow (to prevent the powdered sugar from flying all over!) and working up to high for 30-60 seconds or until well mixed and fluffy. Taste and add more powdered sugar as you like. (I usually use 1 cup.)
- Place 1 ¼ cups of the frosting into a medium bowl. Add 1-2 drops food coloring (this is the top of the rainbow—I used red food coloring here) and stir to combine.
- Divide the remaining frosting into 4 small bowls. Add 1-2 drops of the remaining colors of food coloring to each and stir to combine.
To assemble the cake:
- Carefully place the cake onto a cutting board. Use a serrated knife to cut in half.
- Use the red frosting to coat the middle of one half. Sandwich the other half on and place, cut side down and standing upright, onto a cake stand or platter.
- Use the remaining red frosting to coat the top edge of the cake, hiding the seam.
- Working your way down from the top edge of the cake, add each color of the rainbow. (It’s okay if it’s not perfect!)
- Cut each marshmallow in half with scissors and place the sticky side onto the base of the sides as clouds.
- Slice to serve.
Equipment
Notes
- This cake is best on the day it’s assembled Cover any leftovers with plastic wrap and store at room temperature for up to 2 days or in the fridge for 3-5.
- You can bake the cake the day before you plan to serve it. Let it cool fully on the wire rack, then place onto a plate lined with parchment paper and cover tightly with plastic wrap to make sure it stays fresh. (Or line a large airtight container with parchment paper and cover.) Store at room temperature.
- I used gel food coloring from Wilton for bright colors. Any will work.
- I like these plant-based food colorings.
- A small cake icing spatula is a good tool for adding the frosting, though a butter knife can also work.
- Place candles on top for a birthday cake.
- You may have a little of each frosting color left over.
- Make the cake chocolate using my Healthy Chocolate Cake recipe.
Nutrition
This post was first published May 2021.
I would love to make it for my 3 year old but I am coeliac and want to be able to eat too. Do you have any tips to make it gluten free? Should I just swap to gf flour? Or almond meal?
Thank you
I would recommend the cup for cup gf flour blend from king arthur flour. It will not work with almond flour.
Do the nonpariel style sprinkles that you prefer get soft in the cake or are they crunchy? Thanks!
They’re soft!
My toddler wants this cake for her 3rd birthday, but would love it to be strawberry flavored! Is there any way I can add a strawberry reduction to the batter by altering other ingredients? I’d like to avoid just using strawberry flavoring.
You could grind up freeze-dried strawberries into a powder and add 1 cup to the batter without any other alternations (I think!). That lends great flavor to pancakes so I am thinking it would also work well here. Or maybe strawberry jam between the layers?
My 4 year old enjoyed the cake!! Thanks !
That’s lovely. Would definitely try it 🙂 Your kid looks beautiful She is super excited aboout this cake idea 🙂 Hugs to her. Thank you for the recipe.
I used a little dab of.icing to the marshmallows to pile them on top of one another to create a more realistic cloud form….looked amazing…I still used a cake plate n managed to hang them over the edge of the plate so it seemed like they were floating..
This is so great, thank you! I recently did an exhaustive-feeling search for rainbow cakes and I agree, it is so hard to find ones that aren’t a hidden reveal in the cake interior. Thanks for coming up with a simple way to make the rainbow obvious. One tip: adding the powdered sugar gradually and beating a lot in between keeps the frosting consistency spreadable and helps get away with the lower sugar amount, which is great! Still plenty sweet!
That’s a great tip, thanks for sharing that!