Birthday Funfetti Sheet Cake with Vanilla Buttercream

A slice of confetti sheet cake with vanilla frosting on a small plate.

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Birthday Funfetti Sheet Cake with Vanilla Buttercream

This soft and fluffy funfetti sheet cake is frosted with vanilla bean buttercream! I think this is the ultimate birthday cake, with rainbow sprinkles in every bite.

Prep Time30

Cook Time30

Total Time1

Course: Dessert

Cuisine: American

Diet: Vegetarian

Servings: servings

Calories: 685kcal

Author: Ella Gilbert

Equipment

9x13-inch cake pan
Stand Mixer
Kitchen Scale
Measuring Spoons
Bowl
Whisk
Rubber Spatula
small offset spatula

Ingredients

Funfetti Sheet Cake

⅓ cup unsalted butter room temperature
1 ⅔ cup white sugar
¼ cup neutral oil
4 large eggs room temperature
3 teaspoons vanilla extract
2 teaspoons baking powder
2 tablespoons cornstarch
1 ½ teaspoons kosher salt
3 cups all-purpose flour
½ cup buttermilk room temperature
½ cup rainbow sprinkles

Vanilla Buttercream

2 sticks unsalted butter room temperature
1 tablespoon vanilla bean paste can swap out for extract
¼ teaspoon kosher salt
4 cups powdered sugar
¼ cup heavy cream or whole milk

Metric - US Customary

Instructions

Preheat the oven to 350℉/175℃. Grease and line a 9x13-inch cake pan with parchment paper.
In a stand mixer fitted with the paddle attachment, beat the room temperature butter with the oil and sugar until creamy on medium speed. This will take about 2-3 minutes, and it'll look a bit grainy and fluffy.
⅓ cup unsalted butter, 1 ⅔ cup white sugar, ¼ cup neutral oil
Add the eggs one at a time, beating well and scraping the bowl after each addition.
4 large eggs
Mix in the vanilla extract.
3 teaspoons vanilla extract
In a small bowl, whisk together the flour with the baking powder, cornstarch, and salt.
2 teaspoons baking powder, 2 tablespoons cornstarch, 1 ½ teaspoons kosher salt, 3 cups all-purpose flour
Add ⅓ of the flour mixture, then mix on low. Add ½ the buttermilk. Repeat once more, then end with the flour mixture.
½ cup buttermilk
Gently stir in the rainbow sprinkles.
½ cup rainbow sprinkles
Pour the cake batter into the prepared pan.
Bake for 33-42 minutes, or until a toothpick inserted comes out clean. Let the cakes cool in the pan for 10-15 minutes before removing and letting them cool completely on wire cooling racks.
In a stand mixer fitted with the paddle attachment, or in a large bowl with a hand held mixer, combine the room temperature butter with the confectioners' sugar, salt, and vanilla bean paste on low speed.
2 sticks unsalted butter, 1 tablespoon vanilla bean paste, 4 cups powdered sugar, ¼ teaspoon kosher salt
Increase the speed to medium-high and beat for 2-3 minutes, until light and fluffy.
If the frosting isn't as creamy as you would like, add in the heavy cream or milk and beat on medium speed until spreadable. You might not need all of it!
¼ cup heavy cream
Frost your cooled cake and add more sprinkles - enjoy!

Notes

My recipes have been developed and tested in metric grams. I highly recommend using a weighing scale and measuring out your ingredients the metric way. Just click on ‘metric’ above ingredients.

Room Temperature: I make sure that all of my ingredients are at room temperature before I start the recipe, so pull out all of the ingredients before you start baking.

Rainbow Sprinkles: I recommend using long-stranded sprinkles and not those little balls, those tend to bleed or disappear into the cake batter when baked.

Kitchen Scale: This cake should be measured out with a kitchen scale, especially the flour. Adding too much flour will make this cake dry, and we already have quite a lot of flour and less buttermilk to help suspend the sprinkles!

Salt: If you don’t have kosher salt, halve the amount of salt called for in the recipe. 1 teaspoon kosher salt = ½ teaspoon fine salt. I am using Diamond Crystal kosher salt and not Morton Salt which is much too salty!

Storage: Keep tightly wrapped in the fridge for up to 5 days. Let it come to room temperature before eating.

Making Ahead: You can make the cake layers ahead of time. Bake them and then once completely cooled, wrap in plastic wrap tightly. Store in the fridge for up to 2 days or in the freezer for up to 2 months. If frozen, allow to defrost and come to room temperature before frosting the cake.

Nutrition