Funfetti Sheet Cake
The most celebratory sheet cake! Fluffy and moist vanilla cake with rainbow sprinkles perfectly suspended throughout, baked in a 9x13 pan, then topped with delicious vanilla buttercream and rainbow sprinkles.
Servings 24 slices
Equipment
Ingredients
Funfetti Sheet Cake
- 2 1/2 Cups (265g) sifted cake flour* DIY recipe in notes
- 2 tsp baking powder
- 1/2 tsp baking soda
- 1 tsp salt
- 3/4 Cup (170g) unsalted butter, softened to room temperature
- 1 3/4 Cup (340g) granulated white sugar
- 3 large eggs, room temperature
- 1/2 Cup (120g) sour cream, room temperature
- 1 Tbsp pure vanilla extract
- 1 Cup (240ml) whole milk, room temperature
- 1/3 Cup (60g) rainbow sprinkles*, coated in 1 tsp flour
Vanilla Buttercream
- 1 1/2 Cups (339g) unsalted butter, room temperature
- 5 Cups (600g) powdered sugar
- 1 Tbsp pure vanilla extract
- 3 Tbsp whole milk, room temperature
- pinch of salt, or to taste
- 1-2 drops pink food color gel (optional)
Garnish (Optional)
- 1/4 Cup rainbow sprinkles
Instructions
Make the Funfetti Sheet Cake
- Preheat the oven to 325°F (163ºC). Prepare a 9x13 metal baking pan* by spraying the sides with baking spray and lining the bottom with parchment paper.
- Sift the cake flour first, then measure it out by spooning and leveling it in your measuring cup. Add the sifted cake flour, baking powder, baking soda, and salt into a medium bowl and whisk to combine. Set aside.
- Add the butter and sugar to the bowl of your stand mixer fitted with the paddle attachment (or a large bowl if using a hand mixer), then beat on medium-high speed until light and fluffy, about 4 minutes, scraping down the bowl and paddle once in between. Add the eggs one at a time, mixing for about 10-15 seconds after each addition. Add the vanilla and sour cream and mix for one minute on high speed.
- Turn the mixer off and add the dry ingredients all at once. Mix on low speed until just combined, then add the milk in a steady stream and mix until just incorporated. Scrape down the sides and bottom of the bowl and give it a few stirs by hand to make sure there are no lumps.
- Coat the rainbow sprinkles in 1 teaspoon of flour, then gently fold them into the cake batter. Pour the batter into the prepared baking pan and bake for 30-35 minutes, or until the cake springs back to the touch and a toothpick inserted into the middle comes out clean. Let the cake cool in the baking dish until room temperature.
Make the Vanilla Buttercream
- In the bowl of your stand mixer fitted with the paddle attachment (or with a handheld mixer and large bowl), cream the butter on medium-high until it’s creamy and light (almost white) in color. About 7 minutes.
- Add the powdered sugar a few cups at a time and mix on low speed, scraping down the bowl and paddle and making sure each addition is fully incorporated before adding the next one.
- Add the vanilla, milk, salt, and pink food color gel (if using) and mix on low speed for another minute, or until fully incorporated.
Assembly
- Once the funfetti sheet cake has cooled completely, frost with the vanilla buttercream. To create the look pictured, use half of the vanilla buttercream to frost the cake surface and swipe through the frosting side to side with an angled spatula to create texture. Garnish the surface with rainbow sprinkles, then add the remaining vanilla buttercream into a piping bag fitted with Wilton Tip 6B. Pipe a star border around the edges of the cake and garnish with more rainbow sprinkles.
Notes
*DIY Cake Flour Recipe: To make your own cake flour, spoon and level one cup of all-purpose flour and remove 2 Tbsp. Add 2 Tbsp of cornstarch. Repeat per the amount of cake flour you need, then sift the flour and cornstarch mixture 4 times (don't skip that step!). After sifting, spoon and level to re-measure the amount of cake flour you need. Keep in mind that since store bought cake flour weighs less than homemade cake flour, 2 1/2 cups of homemade cake flour will weigh closer to 331g instead of 265g.
*9x13 Baking Dish: I used a metal pan for this sheet cake, but a ceramic or glass baking dish will work just fine if you add 10-15 minutes to the baking time.
*Rainbow Sprinkles: Be sure to use the elongated rainbow sprinkles (jimmies) and check the ingredients label for "carnauba wax" and "confectioner's glaze". These two ingredients will ensure the sprinkles do not bleed color when folded into the batter.
Make Ahead Tips:
- The funfetti sheet cake can be made ahead and stored at room temperature, covered tightly in plastic wrap, for up to two days. Alternatively, you can cover with plastic wrap and store in the freezer for up to two months before thawing to room temperature.
- The vanilla buttercream can be made ahead and stored in an airtight container at room temperature for up to 1 day. Alternatively, you can store it in an airtight container in the refrigerator for up to two weeks. When you’re ready to use it, bring it back to room temperature and rewhip with your stand mixer to bring back to frosting consistency.
- The frosted sheet cake can be stored at room temperature, covered with plastic wrap or aluminum foil, for up to five days.