Bake a moist Funfetti Cake Recipe with rainbow sprinkles and vanilla buttercream for joyful celebrations.
Preheat the oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing and lightly flouring them so the layers release cleanly after baking. This simple first action sets the stage — warm oven, buttered pans — and keeps the rhythm calm and intentional as you move into the mixing stage.
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until the mixture is even and aerated. Whisking at this stage removes lumps and helps the leavening agents distribute uniformly so the crumb rises evenly.
In a large bowl, beat the softened unsalted butter and granulated sugar together until the mixture is light, pale, and fluffy. Beat long enough to incorporate air — you want a soft ribbon when the beater lifts away — this is where the cake’s tender crumb begins.
Add the eggs one at a time to the creamed butter and sugar, beating well after each addition so the batter stays emulsified and smooth. Stir in the vanilla extract for fragrance; the batter becomes glossy and unified as the eggs fully incorporate.
Add the flour mixture and the sour cream to the butter mixture in alternating additions, beginning and ending with the flour mixture. Fold gently and mix only until just combined so the batter remains tender — overmixing can tighten the crumb.
Stir in the milk to loosen the batter slightly, then gently fold in the rainbow sprinkles until they are evenly distributed without streaking. The batter should be smooth, thick but pourable, speckled with tiny colorful dots that promise the playful interior of the cake.

Divide the batter evenly between the two prepared pans, smoothing the tops lightly with a spatula. Bake for 25–30 minutes until a toothpick inserted in the center comes out clean and the tops are lightly golden — the layers will spring back slightly when ready.
Allow the cakes to cool in their pans for about 10 minutes, then carefully invert them onto wire racks to cool completely. Cooling fully ensures the frosting won’t melt and the layers remain stable as you assemble.
Beat the softened butter for the frosting until creamy and aerated, creating a light foundation for the icing. This short step transforms the butter into a silky base that will take the powdered sugar smoothly.
Gradually add the sifted powdered sugar to the creamed butter, beating until the mixture is smooth and lump-free. You should achieve a thick, spreadable frosting that still feels silky on the spatula.
Mix in the vanilla extract, then add heavy cream one tablespoon at a time until the frosting reaches your desired spreadable consistency — creamy, glossy, and pipeable if you like a cleaner edge.
Once the cake layers are completely cool, stack and frost them with the vanilla buttercream, smoothing the sides and top for a clean finish. Decorate generously with additional rainbow sprinkles, and remove a slice so the interior mosaic of sprinkles is visible. The finished cake should look tender, richly frosted, and celebratory — with stray sprinkles and a few crumbs around the plate for a natural, joyful finish.
