Rainbow Cookies with rainbow swirl buttercream frosting for Camille’s birthday party!

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

Camille’s 3rd birthday is coming up, and the theme is RAINBOWS! All the rainbows, all the sprinkles.

It’s times like these when I’m so glad I have a daughter, because making a cake look like a super hero or a truck seems WAY harder than a tub of sprinkles and some rainbow frosting.

If you’re thinking that these rainbow cookies look suspiciously similar to my Christmas Lights cookies, that is because cookie decorating is not one of the talents I was not blessed with, unfortunately.

I know that practice makes perfect, but I also lack the patience to work through the dozens of pounds of butter while I hone my piping skills. Talent-less and laziness, what a winning combo, right?

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

When I need to make cute cookies, I go with something simple, like a little cookie with a white base. This way, the simple decorations pop on the white background. These simple small-batch cut out sugar cookies topped with a small batch of royal icing are the perfect blank canvas for embellishments.

First, I made a small batch of my cut-out sugar cookies, and topped them with my small-batch royal icing recipe that uses just 1 egg white, 2/3 cup of sugar and 2 teaspoons of lemon juice. This royal icing has a consistency that is easy to spread with the back of a knife and doesn’t run much over the sides. It’s a low-maintenance royal icing that doesn’t require piping. I love it, and use it often.

Rainbow Cookies Recipe with Rainbow Swirl Buttercream Frosting with Royal Icing base

Then, I made a batch of plain buttercream using just 1 stick of butter (the recipe only makes 11-12 cookies, perfect for party favor bags!), and then divided it into 6 bowls. I tinted each bowl red, orange, yellow, green, blue and purple.

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

Once I had all of the colors, I made stripes of the colors on a big sheet of plastic wrap.

Then, I carefully rolled up the plastic wrap into a tube, and twisted the ends closed. I snipped off one end, and placed the entire bag inside a piping bag fitted with a tip. I used the Wilton 105 tip. (<–link to it!)

Yes, the plastic wrap stays inside the piping bag, and everything is fine! Everything is perfect! Rainbow cookies for everyone!

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

Finally, I piped little rainbows on one end each cookie. I topped the rainbows with gold sprinkles (<–link to the exact ones I used) and a few gold drags on one side of each rainbow.

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

These rainbow cookies are going in the goody bags at Camille’s birthday party, and I can’t wait to show you!

There might be a rainbow baby smash cake coming your way. Wait, do 3 year olds smash cakes?

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

Yield: 11 cookies

Rainbow Cookies

Rainbow Cookies with rainbow swirl buttercream frosting and a white Royal Icing base

Rainbow cookies with rainbow swirl buttercream frosting!

Prep Time 1 hour
Cook Time 12 minutes
Total Time 1 hour 12 minutes


  • 3/4 cup flour, plus extra for rolling
  • 1/2 teaspoon baking powder
  • pinch of salt
  • 1/4 cup unsalted butter, softened
  • 1/4 cup sugar
  • 1 egg yolk
  • 1/2 teaspoon vanilla
  • 1/4 teaspoon almond extract

For the small-batch royal icing:

  • 1 1/2 cups powdered sugar
  • 2 teaspoons fresh lemon juice
  • 1 large egg white

For the rainbow buttercream:

  • 1 stick of unsalted butter, softened
  • 2 1/2 cups powdered sugar
  • 1 tablespoon heavy cream
  • 1 teaspoon vanilla extract
  • red gel food coloring
  • yellow gel food coloring
  • blue gel food coloring


  1. In a small bowl, whisk together the flour, baking powder and salt.
  2. In a medium bowl, beat together with an electric mixer the butter and sugar. Once light and fluffy, add the egg yolk and vanilla and almond extracts.
  3. Once well incorporated, sprinkle over half the flour mixture and beat gently until combined, then sprinkle over the rest. Beat until no streaks of flour remain, but be careful not to over-mix.
  4. Dust a clean counter top with flour, and dump the dough out onto it. Gather it into a ball and press it into a 1/2" thick round disk. Flour your rolling pin, then roll out the dough out big enough to cut out about 8 shapes using a 4" round cookie cutter. Place the shapes on a baking sheet lined with parchment paper or a silicone mat. Gather the dough scraps and re-roll to cut out 4 more shapes and place them on the cookie sheet. You should get 12 cookies.
  5. Place the cookie sheet in the freezer for the minutes while you preheat the oven to 350.
  6. Once the oven is hot, bake the cookies for 10-12 minutes, until the edges of the cookies just start to turn brown. Let them sit on the sheet a few minutes before moving them a wire rack to cool completely.
  7. Once the cookies are cooled completely, make the royal icing: in a small bowl, combine the powdered sugar and lemon juice.
  8. Beat the egg white in a small bowl to loosen it, and then measure out 2 tablespoons of egg whites and add them to the bowl with the sugar.
  9. Whisk together the icing, starting slowly, and trust that the sugar will melt and it will become liquid. Resist the urge to add any more liquid to the bowl, and instead just keep whisk slowly.
  10. When the icing comes together, spoon a small amount onto each cookie, and use an off-set spatula to spread it almost to the edges.
  11. Let the royal icing harden completely on the cookies before proceeding.
  12. Next, make the rainbow buttercream: beat together with a hand-held electric mixer on medium the butter, powdered sugar, heavy cream, vanilla until light and fluffy.
  13. Divide the frosting into 6 bowls.
  14. Using the food gels one drop at a time, tint one bowl red, tint one bowl orange (one drop of red plus one drop of yellow), tint one bowl yellow, tint one bowl green (one drop of yellow plus one drop of blue), tint one bowl blue, and tint one bowl purple (one drop of red plus one drop of blue). Adjust the vibrancy of the colors to your liking using extra food coloring.
  15. Lay a 12" square piece of plastic wrap in front of you. Using a small spoon, make lines with the frosting (see the picture). Try to make the lines as long and narrow as possible. I like to go in rainbow order: red, orange, yellow, green, blue and purple.
  16. Gently roll the plastic wrap up into a tube, and then twist the ends closed.
  17. Snip off one end of the plastic wrap, and drop it into a piping bag fitted with a XX tip.
  18. Make a practice rainbow on a piece of scrap paper to make sure you're ready to go. Then, pipe rainbows onto all of your cookies.
  19. Decorate with gold sprinkles and gold dragees at the end of the rainbows.


*The frosting recipe makes about twice as much frosting as you actually need for these cookies. I used it on Camille's rainbow birthday cake, but know that you could halve the recipe if you don't want any leftovers.

Nutrition Information:



Serving Size:


Amount Per Serving: Calories: 333Total Fat: 14gSaturated Fat: 8gTrans Fat: 0gUnsaturated Fat: 5gCholesterol: 68mgSodium: 45mgCarbohydrates: 51gFiber: 0gSugar: 44gProtein: 2g

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