Easy Rainbow Cake Recipe

Rainbow cakes make everyone happy. It's just a fact of life. This rainbow cake will make you extra happy because it uses boxed cake mix for the easiest (but still amazingly delicious!) way to make such a fun cake.

It's my birthday today, and I'm so thankful for another year around the sun. Another year to do good things. Another year to raise my babies. Another year to laugh and learn. I'm thankful for it all.

We've really been celebrating since yesterday. Connor set up a whole classroom in the basement, and he celebrated my birthday exactly how they celebrate in his Kindergarten class, except I got a smorgasbord of an iced cookie, fortune cookie, or ice cream from the play kitchen. We had a mystery reader (surprise! It was me!) to read The Book with No Pictures, which is a favorite in our household. I got to stand at the front of the class while my best friend and two children sang me happy birthday. Then I was presented with a drawing Connor had been working on all afternoon. Finally, as if there could be any cuter ways to celebrate a birthday, the teacher declared me the line leader (behind him, of course) to head back up the stairs to put jammies on and get ready for bed. That was a pretty solid birthday before my actual birthday, if you ask me.

This rainbow cake recipe is magical for toddlers, y'all.

The kids went nuts over this rainbow cake. It was like I had made unicorns and narwhals pop out from their dessert. It was magical! Bri also didn't get the memo about just looking at the rainbow cake. I told her to "just look" as I was taking photos and she had some confirmation bias and interpreted that as "just lick." She got to lick a brand new cake (thank God it was meant for us) and I got the cutest picture ever.

Don't be fooled though. 95% of the time when I'm snapping pictures, they look like this.

Let's chat about some of the basics so you feel confident in making this cake at home.

Hallelujah for rainbow cake using boxed cake mix

This cake uses boxed cake mix. I'll say it again -- BOXED CAKE MIX! This cake cost me less than $10 to make. That's about $65 less than any rainbow cake you'd buy at a bakery, and it really doesn't take a lot of effort. Anytime I do something more complicated than making a regular ole cake, I always look for shortcuts because you're already going above and beyond. Cut yourself some slack.

Materials needed for this rainbow cake:

• 3 boxes of white cake mix. Any brand, any variety you prefer. I used Duncan Hines, but it doesn't really matter.
• Gel-based food coloring. See below for more details but this is really necessary.
• Six 8" cake pans. Don't worry if you only have two, no biggie. It'll just take you a lot longer because you'll have to bake in batches and wait for the cakes to cool.
• 1 can of white frosting. Make sure you don't get cream cheese or vanilla. While those are delicious choices, they won't be that vibrant white color. Be sure to get the good ole white frosting. Also note that the frosting covers enough for a "naked cake," meaning one that's barely frosted on the outside. If you want a fully covered cake, you'll definitely need to buy at least 2 cans of frosting.
• OPTIONAL: A pastry bag and Wilton tip #4 is what I use to pipe a thin layer of frosting between each of the layers. You certainly could use a plastic bag that you cut off the end of to pipe on the cake. This just makes it neater and easier to do quickly for me.

The best food coloring to use

It goes without saying, food coloring is a big part of this rainbow cake. That's what gives the cake the bright colors of the rainbow.

If you're looking for the bright, bold rainbow colors, you have to use gel food coloring. It's really the only way I've found to get those vibrant colors. I love the Wilton gel food coloring in particular.

If you're looking for a more natural food dye, you can try plant-based food coloring. I have never used this dye for this cake, so I can't speak to how it will turn out, but the colors will be much more muted. It would still be pretty but not nearly as bright.

How to make a rainbow cake

Here are a few simple, step-by-step directions for making your easy rainbow cake from your boxed cake mix!

1. Preheat your oven to 325 degrees F, and spray six 8" round cake pans with non-stick cooking spray. Line the bottoms of each pan with parchment paper to prevent any possibility of sticking. This is really necessary, as you'll want your layers to come out of the pan nicely.

2. Make your cake according to package directions. Get the biggest bowl you have in your house, and make a triple batch of your cake in that one bowl according to the package directions. There's no need to use a mixer. Don't mix the batter that well until the dye is in. You'll have to naturally do a lot more mixing to spread the color evenly, and you don't want to over mix the cake batter.
3. Measure batter evenly into each of 7 bowls (Yes, 7. I'll explain why in a second). Start with a cup of your cake batter in each bowl. Once the batter has been evenly distributed in each of the bowls, go for a second cup of batter in each. Depending on what boxed cake mix you use, you're looking at no more than 2 ½ cups of cake batter per bowl. This'll ensure you have even layers to your rainbow cake.
4. Slowly add the gel food coloring with a clean toothpick little by little into each of the bowls. Don't forget the colors of the rainbow: ROY G. BIV (except we don't do indigo around here). It's easy to get the red, blue, and yellow to be vibrant, but once you start making purple (blue and red), green (yellow and blue), and orange (yellow and red), this'll get trickier. The good thing about the gel food coloring is that it has most of these colors already mixed for you. Go easy on the darker colors (like blue when making green). Keep stirring until there are no streaks of batter. Add more color as needed bit by bit.

5. Pour batter into each of your 6 cake pans or do this step in batches and bake for only about 10 minutes for layer. Once a toothpick comes out clean, take it out of the oven. Let the cakes rest for 10-20 minutes before gently flipping over onto a cooling wrack. Cool completely before frosting.

The 7th Bowl

The 7th bowl is your "oh sh*t" bowl. When you mix colors, sometimes it's easy to make a mistake and put too much of one color. This happened to me when making the orange. I put too much red in initially. No biggie. You have a chance to try again because of this 7th bowl as a back-up. Maybe you won't need it, but it's come in handy for me on at least one occasion.

Tips on frosting your cake

If you've been following me and have read my post for Homemade Strawberry Cake and Nothing Bundt Cake copycat recipe, you know that I am on a full frosting hiatus. And I'm predicting that hiatus won't be up for quire some time -- perhaps when the kids move out of the house?

That doesn't mean you can't have a beautiful cake though. I think a naked, thin layer of frosting gives the cake rustic beauty, like it's wild and free from the constraints of society. Or I'm just way too lazy to finish the cake.

More Cakes You'll Love

If you love this cake, check out these other cake recipes you'll also love.

xox

kathryn