This is the easiest and tastiest DIY rainbow cake topper you’ll find! Using a cookie to top your cake is a really fun way to wow your kiddo, especially if, like me, you have little to no cake decorating skills but a fair hand at M&M placement. And who doesn’t love edible decor?
For Aidan’s fifth birthday he requested a My Little Pony/Transformer mash-up party. I made one Transformers banner and then fully embraced the My Little Pony rainbow extravaganza for everything else, haha. He even wore a Yippitee rainbow 5 shirt! (Last year he was superheroes all day every day so he wasn’t interested in a Yippitee shirt. So my mompreneur heart did a little happy dance when he asked me for one this year.)
DIY Rainbow Cake Topper Tutorial
For this tutorial, you can freehand a rainbow or use my free template linked below to make your rainbow shaped cookies. You’ll need your favorite sugar cookie recipe or premade dough and royal icing. Cookies that don’t spread or puff up when baking work best. I am a chocoholic so I used this chocolate sugar cookie recipe and my favorite simple royal icing recipe.
- Rainbow template (originally in this post)
- Wax paper
- Sharp knife
- Cookie dough
- Royal icing
- Mini M&Ms or other small colorful candies or sprinkles
- When buying your candies aim for the size of mini M&Ms as those fit my template perfectly. If you want to use larger or smaller candies you can also print the rainbow template at a larger or smaller scale. Just test how many fit in a row before adding your icing.
- On timing: royal icing needs time to set – at least a few hours. So aim to make the cookies the day before your party!
1. Separate your candies by color to make it easier to place them quickly on your iced cookie when time. This is a fun part for kids to help with! (I let Aidan eat all the brown M&Ms so finding those became his first priority…)
2. Make your favorite sugar cookie dough according to its usual directions. (My favorite chocolate sugar cookie recipe is here.) While it’s chilling in the fridge you can create your rainbow template.
3. Download my free rainbow unicorn cake topper. Print it on regular paper. I used the 6.75″ size for my 9″ round cake.
4. Place a piece of wax paper on top and trace just the rainbow – you’ll have to estimate the bottom left side where the unicorn is. I used wax paper so that it would be easy to see through for tracing. You could also cut the rainbow directly from the printed template if you want. (I wasn’t sure how I felt about putting paper that ran through my printer onto cookie dough but that may be overly cautious.)
5. Roll your cookie dough out to your desired thickness, at least 1/4″ so it’s sturdy enough to hold up with all the candies on top.
6. Place your wax paper template on top and cut around it with a sharp knife. I cut two so that I had a backup rainbow in case one broke before birthday cake time. I didn’t end up needing it but I recommend this just to be safe!
7. Carefully add one toothpick halfway into the center of each side of the bottom of the rainbow. I forgot this step and my rainbow tilted a few times at the party before it was cake time.
8. Chill and bake the cookie dough according to your recipe’s instructions.
9. While it’s baking or cooling, mix up your royal icing. I use this recipe. Note the tip to place a damp towel over the top of your royal icing bowl to avoid it getting a hard crust.
10. Test how your candies will fit on your cookie before you ice it. Mini M&Ms were the perfect size for me to fit red, orange, yellow, green, and blue.
11. When your cookies are cool and you’re ready to add the candies quickly (meaning they’re already separated by color and nearby), spread your icing on the cookie. I kept mine at a pretty thick consistency and spread it on with a knife.
12. Add your candies or sprinkles. Let the icing dry completely before moving it (at least a few hours, up to overnight).
13. Don’t add your cookie to your cake until it’s in its final party destination.
14. For the cake, I frosted the whole thing with blue buttercream and then piped some white clouds scattered around. I piped bigger clumps of clouds at the top where I knew I would add the rainbow so that it would be a quick pop in when we were at the playground for his party. To do this I held the cookie right over the cake and marked with a knife where to make the clouds.
15. Once you’re at your final location, pop the cookie into the cake by the clouds.
I hope the cake is a big hit! If you manage to get pictures in all the madness of party planning, please share! You can tag me on Instagram or Facebook. (I’ll only see your tags if your account is public so send me a message if I don’t comment!)
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