This Rainbow Funfetti Birthday Sheet Cake recipe yields a plush funfetti sheet cake studded with rainbow sprinkles and topped with rainbow cream cheese swiss meringue buttercream. This moist vanilla confetti cake is a perfect centerpiece dessert for a birthday or pride.
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June is my favorite month because it's my birthday month and pride month! This funfetti cake recipe is adapted from the Milk Bar birthday cake original recipe, which is my ideal birthday cake. I add toasted milk powder to the cake and buttercream for even more bakery-quality flavor. I also swapped the grapeseed oil for avocado oil, but you can really use any neutral-flavored oil. I top it off with a naturally-colored Swiss meringue buttercream rainbow.
If Swiss meringue buttercream isn't your thing, my pride funfetti layer cake has an easier traditional cream cheese frosting recipe with lemon juice for extra tang. And if you don't feel like layering with that recipe, you could bake it in an 8x8-inch square pan as a snack cake! Another rainbow favorite of mine is this rainbow fruit tart, that uses lots of fresh fruit for the rainbow motif.
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Why you'll love this recipe
- The addition of toasted milk powder adds a malty creamy flavor to the entire cake.
- The crumb is tender and moist!
- This sheet cake version is so much easier to make and decorate than a layered cake.
Ingredients
- Granulated sugar sweetens the cake and the buttercream.
- Light brown sugar also sweetens the cake.
- Cake flour provides a tender crumb to the cake.
- Oil, unsalted butter and vegetable shortening provide richness and moisture. I used avocado oil, but any neutral-flavored oil will work, including vegetable oil, canola oil, grapeseed oil or sunflower oil.
- Toasted milk powder adds nuttiness and deeper flavor to the cake and buttercream. To toast milk powder, constantly stir it in a clean pan over medium heat until golden brown.
- Clear vanilla extract provides that irreplaceable boxed cake mix flavor. I do not recommend subbing for regular vanilla extract. It will not give the same effect.
- Buttermilk adds tang, richness and moisture to the cake.
- Rainbow funfetti sprinkles add a pop of color and fun to the cake.
- Large eggs give structure to the cake and buttercream.
- Kosher salt balances the overall flavor, making for a dessert that's not overly sweet.
- Baking powder gives rise to the cake.
- Cream cheese flavors the buttercream with tang.
See recipe card below for a full list of ingredients and measurements.
Substitutions and variations
Here's how to customize this rainbow funfetti birthday sheet cake to your liking:
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- Cake soak — the original Milk Bar recipe recommends soaking the cake layers with a mixture of ¼ cup (55g) milk and 1 teaspoon vanilla extract (4g). If you plan to make this cake ahead of time or store it for awhile, I recommend adding the soak to keep the cake moist for longer.
- Layered cake — To make a layered cake from this recipe, bake the batter in two round 8-inch cake pans. I recommend adding the cake soak (above) for a layered cake.
- Almond extract — a touch of almond extract would be great in the cake and/or buttercream. I recommend ¼-1/2 teaspoon for each.
- No cake flour — to swap the cake flour for all-purpose flour use 2 tablespoons less all-purpose flour than what is called for in cake flour.
- All-natural dyes — use naturally-dyed sprinkles in the cake batter.
- Funfetti cupcakes — to use this recipe for cupcakes, use the same oven temperature, but begin checking for doneness at 15 minutes as the bake time will be shorter. It should yield about about 24 cupcakes.
- Whipped cream — instead of buttercream, top the cake with whipped cream. Whip 2 cups of heavy cream with ¼ cup of powdered sugar and 1 teaspoon of vanilla extract until soft peaks.
- No sprinkles — if colorful sprinkles aren't your thing, feel free to omit them for a plain, delicious white cake recipe.
This recipe has not been tested with any substitutions or variations. If you try any, please let me know how it turned out by commenting below!
How to make rainbow funfetti birthday sheet cake
Step 1: Grease a 9x13 metal cake pan. If you want to remove it from the pan for presentation, line the pan with parchment paper with overhang for easier removal. Preheat the oven to 350°F. In a medium mixing bowl, whisk together the cake flour, milk powder, baking powder, salt and sprinkles. Set aside the flour mixture.
Step 2: In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl with an electric mixer, add the butter, shortening and both sugars. Beat on medium-high speed for 2-3 minutes, or until fluffy and lighter in color. Be sure to scrape the sides of the bowl throughout the mixing process. Add the eggs and beat for another 2-3 minutes. Mix on low speed and stream in the buttermilk, oil and vanilla. Increase the speed to medium-high and mix for 4-6 minutes. The mixture should become lighter in color, doubled in size and homogenous. Add the whisked dry ingredients and mix just until combined.
Step 3: Pour the batter into the prepared pan, smoothing to the edges with an offset spatula. Scatter the remaining 2 tablespoons of sprinkles on top. Bake for 33-35 minutes or until a cake tester or toothpick inserted in the center of the cake comes out clean. Let cool in the pan completely before icing. If removing from the pan, remove to a wire rack after 30 minutes to cool. As the cake cools, make the buttercream.
Step 4: Make the swiss meringue buttercream according to Serious Eats’ instructions. Remove the Swiss meringue buttercream from the mixer bowl to a separate large bowl. Add the cream cheese to the mixer bowl that the buttercream was in. Beat until smooth. Add the vanilla extract and milk powder and beat to combine. Gradually add the swiss meringue buttercream to the cream cheese mixture, beating on medium speed to combine. Divide the buttercream evenly between 6 bowls. Keep one medium bowl white and color each of the remaining bowls (pink/red, orange/yellow, green, blue, purple). If using natural food coloring, sometimes it is easier to wet the powders with a bit of vanilla extract to make a paste before adding it to the buttercream. I also used an immersion blender to get a smoother consistency on some of them. I used 2 teaspoon raspberry juice powder and ½ teaspoon hibiscus powder for the pink/red frosting, 3 teaspoon mango juice powder and ½ teaspoon turmeric for the orange/yellow frosting, 1 teaspoon butterfly pea powder for the blue frosting, 2 teaspoon purple sweet potato powder for the purple frosting and 1 ½ teaspoon matcha for the green frosting. Spread the white frosting on top of the cake in a thin layer with an offset spatula. Pipe the remaining frostings on using a wide raked piping tip. Garnish as desired.
Top tips
- Do not overmix the cake batter after adding the dry ingredients. If you overmix, the crumb will be less tender.
- To substitute the cake flour for all-purpose flour, use 2 tablespoons less of all-purpose flour.
- Don't swap the clear vanilla extract for regular brown vanilla extract. The flavor will not be the same!
- Be sure to use room temperature ingredients when baking, unless otherwise specified.
Recipe FAQs
Store the cake in an airtight container in the refrigerator for 2-3 days. Let come to room temperature before serving. If freezing, wrap tightly in plastic wrap and store for 2 months.
I do not recommend this. If you prefer a cake with egg whites only, I recommend this white cake.
I do not recommend this.
More recipes you'll love
Lastly, if you make this Rainbow Funfetti Birthday Sheet Cake recipe be sure to leave a comment or give it a rating. I love to see when people make my recipes, so please tag me @youthsweets on Instagram if you post!
📖 Recipe
Rainbow Funfetti Birthday Sheet Cake
Equipment
Ingredients
Cake
- 2 cups cake flour (245g)
- 2 tablespoon milk powder toasted* (14g) optional
- 1 ½ teaspoon baking powder (6g)
- ¾ teaspoon kosher salt (3g)
- ¼ cup + 2 tablespoon rainbow sprinkles divided (75g)
- 4 tablespoon unsalted butter room temperature (55g, ½ stick)
- ⅓ cup vegetable shortening (60g)
- 1 ¼ cup granulated sugar (250g)
- 3 tablespoon light brown sugar packed (50g)
- 3 large eggs
- ½ cup buttermilk (110g)
- ⅓ cup neutral oil (65g)
- 2 teaspoon clear vanilla extract (8g) do not sub for regular vanilla
Cream cheese swiss meringue buttercream
- 1 batch Swiss meringue buttercream from Serious Eats’
- 8 oz cream cheese room temperature
- 2 teaspoon clear vanilla extract
- 1 tablespoon milk powder toasted (7g) optional
- Gel food coloring or natural food coloring (mango juice powder, turmeric, butterfly pea powder, purple sweet potato powder, raspberry powder, hibiscus powder, matcha)
Instructions
Do ahead
- Grease a 9x13 metal cake pan. If you want to remove it from the pan for presentation, line the pan with parchment paper with overhang for easier removal.
- Preheat the oven to 350°F.
Make the cake
- In a medium mixing bowl, whisk together the cake flour, milk powder, baking powder, salt and sprinkles. Set aside.
- In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl with electric beaters, add the butter, shortening and both sugars. Beat on medium-high for 2-3 minutes, or until fluffy and lighter in color. Be sure to scrape the bowl throughout the mixing process. Add the eggs and beat for another 2-3 minutes.
- Mix on low and stream in the buttermilk, oil and vanilla. Increase the speed to medium-high and mix for 4-6 minutes. The mixture should become lighter in color, doubled in size and homogenous.
- Add the whisked dry ingredients and mix just until combined.
- Pour the batter into the prepared pan, smoothing to the edges with an offset spatula. Scatter the remaining 2 tablespoons of sprinkles on top.
- Bake for 33-35 minutes. Let cool in the pan completely before icing.
Make the frosting
- Make the swiss meringue buttercream according to Serious Eats’ instructions.
- Remove the Swiss meringue buttercream from the mixer bowl to a separate bowl. Add the cream cheese to the mixer bowl that the buttercream was in. Beat until smooth. Add the vanilla extract and milk powder and beat to combine.
- Gradually add the swiss meringue buttercream to the cream cheese mixture, beating to combine.
- Divide the buttercream evenly between 6 bowls. Keep one bowl white and color each of the remaining bowls (pink/red, orange/yellow, green, blue, purple).
- If using natural food coloring, sometimes it is easier to wet the powders with a bit of vanilla extract to make a paste before adding it to the buttercream. I also used an immersion blender to get a smoother consistency on some of them.
- I used 2 teaspoon raspberry juice powder and ½ teaspoon hibiscus powder for the pink/red frosting, 3 teaspoon mango juice powder and ½ teaspoon turmeric for the orange/yellow frosting, 1 teaspoon butterfly pea powder for the blue frosting, 2 teaspoon purple sweet potato powder for the purple frosting and 1 ½ teaspoon matcha for the green frosting.
Assemble
- Spread the white frosting on the cooled cake with an offset spatula. Pipe the remaining frostings on using a wide raked piping tip.
- Garnish as desired.
Notes
Nutrition
Originally published 06/27/2025.
This is as close to that iconic box mix vanilla flavor as you can get and I love the fluffy texture. Full disclosure, I am the author of this recipe.