Ultimate Funfetti Birthday Cake with Rainbow Decoration
Baking,  Recipes,  Sarah

Ultimate Funfetti Birthday Cake

Rainbow Ultimate Funfetti Birthday Cake SliceBirthdays are so special! Jessica & I are both Leos & our birthdays are only a few days apart. When it comes time for the birthday season, we are ready! This Ultimate Funfetti Birthday Cake is fun, delicious & a great centerpiece for any celebration. It’s our take on the classic Funfetti cake. Except our recipe features homemade sprinkles, a buttery & rich buttermilk cake & a thick & creamy buttercream icing.

Funfetti Layer Cake


This recipe is a take on Joy The Baker’s Birthday cake recipe. Well, one time I added in double the butter – oops! I added in a bit more sugar & took a chance. Well, my friends, it paid off. This cake is so rich, I will eat it without frosting. That says a lot coming from me. While the cake recipe makes 3 9 inch cakes, I recommend making a two-tier cake & saving the third cake to make yourself some Birthday Cake Ice Cream.

Buttermilk Funfetti Layer Cake

Stack these puppies & be sure to put plenty of sprinkles in the batter & in between the layers. An Ultimate Funfetti Birthday Cake needs to scream with color, happiness & rainbows!


Rainbow icing Satisfying Since there is plenty of leftover royal icing from our homemade sprinkles, we decided to try something new! If you take the royal icing, you can spread it in any combo. Once you let it dry, you can use it to decorate!

You can make it thicker or thinner. Obviously, the thicker pieces take longer to dry, but they are easier to handle & less likely to break. I’m so excited it turned out well. I’m looking forward to decorating with more royal icing in the future.

Annabelle told me I had to get it on video because it is so satisfying to watch. I have to tell you. I totally agree!


Let’s put the finishing touches on the Ultime Funfetti Birthday Cake! Top the cake with loads of sprinkles & put plenty of sprinkles on the side of the cake as well. Since we tried the royal icing trick, I opted to make a mosaic of sorts to decorate the sides.

Buttermilk Cake with Buttercream Frosting

Since I cannot leave well enough alone, I stuck some of the royal icing decorations into the top of the cake. To me, they look like feathers, but more than that, they look fun! It’s like this cake is reaching out saying in it’s best Jeff Spicoli voice, “let’s party!”

Funfetti Birthday Layer cake

Cut into the cake & get the party started. It’s birthday time, friends!

Ultimate Funfetti Birthday Cake Slice

Funfetti Birthday Layer cake
5 from 1 vote

Ultimate Funfetti Birthday Cake

It's time to celebrate with this buttermilk cake with a vanilla buttercream icing chock full of sprinkles.

Course Dessert
Cuisine American
Prep Time 20 minutes
Cook Time 30 minutes
Servings 12 servings


  • 1 cup (2 sticks) of unsalted butter softened
  • 2 1/2 cups granulated sugar
  • 3 large eggs
  • 2 teaspoon pure vanilla extract
  • 2 1/4 cups all-purpose flour
  • 2 teaspoons baking powder
  • 1 teaspoon baking soda
  • 1 teaspoon salt
  • 1 1/4 cups buttermilk
  • Vanilla Buttercream Frosting
  • 1 cups (2 sticks) of unsalted butter at room temperature
  • 3 to 4 cups confectioners’ sugar sifted
  • 1 1⁄4 teaspoon salt
  • 2 teaspoons pure vanilla extract
  • 3 to 4 tbsp heavy cream or milk


  1. To make the cake, place a rack in the center of the oven and preheat oven to 350 degrees Grease and flour 3 9 inch pans.
  2. Cream together butter and sugar until light and fluffy, about 3 to 5 minutes.
  3. Stop the mixer and scrape down the sides of the bowl. Beat in the eggs, one at a time, beating for 1 minute between each addition. Beat in vanilla extract.

  4. In a medium bowl whisk together flour, baking powder, baking soda, and salt. Add the dry ingredients all at once to the butter and egg mixture and beat on low until just combined. Add the buttermilk and beat on low for 1 minute. Increase the speed to medium and beat for 3 minutes more.
  5. Pour batter into prepared pans. Bake for 25 – 30 minutes or until cooked through and the top springs back lightly when touch. Test the cake by inserted a skewer into the center of the cake. The cake is done when just a few crumbs are left on the skewer.

  6. Remove from the oven and allow to cool in the pan for ten minutes & then transfer to a cooling rack. Let the cake cool completely before adding frosting. Keep the third cake for some Birthday Cake ice cream or go all out with a 3 tiered cake.
  7. In the bowl of an electric mixer fitted with the paddle attachment, beat the butter on medium speed until soft, about 1 minute. Add in 2 cups of the confectioners’ sugar. Then, add the salt and vanilla.

  8. Beat on low speed until the sugar is well incorporated. Add in the cream/milk. Add remaining 1-2 cups of sugar as needed to thicken the frosting. Beat on medium speed until the frosting is smooth and fluffy, about 4 minutes.
  9. Stack the cake, add layer of buttercream & add sprinkles. Stack the second layer, add additional icing and tops with additional sprinkles.






Momma, wife, baker, reader & smart ass. I am Really Into doughnuts, inside jokes, trash TV, pizza, 48 Hours & George Michael.


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