Three-Layer Funfetti Birthday Cake with Vanilla Buttercream

Funfetti Birthday Cake

Three layers of soft vanilla cake, dotted with rainbow jimmies and separated by thin lines of white buttercream, make this Funfetti cake stand tall when sliced. The batter uses both butter and oil, with buttermilk for a tender crumb.

Bake the layers in three 8-inch round pans at 350°F (175°C). Fold the jimmies in last to limit color streaks, and let the cakes cool completely before frosting. Start checking at 28 minutes rather than relying on the bake time alone.

Makes 12–16 slices. Allow about 45 minutes for preparation, 30–35 minutes for baking, and about 2 hours 30 minutes total, including cooling and assembly.

Ingredients

For the cake

• 3 cups cake flour (360g)
• 1 3/4 cups granulated sugar (350g)
• 2 1/2 teaspoons baking powder
• 1 teaspoon fine salt
• 1 cup unsalted butter, softened (225g)
• 1/3 cup neutral oil (75g)
• 4 large eggs, at room temperature
• 1 cup buttermilk, at room temperature (240g)
• 2 teaspoons vanilla extract
• 3/4 cup rainbow jimmies (120g)

For the vanilla buttercream

• 1 1/2 cups unsalted butter, softened (340g)
• 5 cups powdered sugar (600g)
• 2 teaspoons vanilla extract
• 1/4 teaspoon fine salt
• 3–5 tablespoons heavy cream or whole milk, as needed

Optional: 1–2 tablespoons extra rainbow jimmies for the top.

How to Make Funfetti Birthday Cake

1. Prepare the pans: Preheat the oven to 350°F with a rack in the center. Grease three 8-inch round cake pans, line the bottoms with parchment rounds, and lightly grease the parchment.
2. Combine the dry ingredients: Whisk the cake flour, baking powder, and salt together in a bowl.
3. Mix the batter: Beat the softened butter and sugar until light and fluffy. Beat in the oil, then add the eggs one at a time. Mix in the vanilla. Add the dry ingredients in stages, alternating with the buttermilk. Scrape the bowl as needed and stop mixing when no dry streaks remain; overmixing after adding flour can make the cake dense.
4. Add the jimmies: Gently fold them into the batter with a spatula. Divide the batter evenly among the prepared pans.
5. Bake: Set the pans on the center rack without crowding them and bake uncovered for about 30–35 minutes. Start checking at 28 minutes. The centers should spring back when gently pressed, and a toothpick inserted in the center should come out clean or with a few moist crumbs, not wet batter. Rotate the pans once if your oven bakes unevenly. If the tops brown before the centers are set, tent them loosely with foil.
6. Cool: Leave the cakes in their pans for about 10 minutes. Turn them onto cooling racks, remove the parchment, and let them cool completely before frosting.
7. Make the buttercream: Beat the softened butter until smooth. Gradually beat in the powdered sugar, then add the vanilla and salt. Beat in 3 tablespoons of cream or milk, adding more as needed until the frosting spreads easily but still holds its shape.
8. Stack and frost: Place one layer on a serving plate and spread a thin, even layer of buttercream over it. Add the second layer and repeat, then set the third layer on top. Spread a thin crumb coat over the top and sides and chill briefly until set. Finish with a light, smooth coat of buttercream. Add a few extra jimmies on top, if desired.
9. Slice: Cut tall slices, wiping the knife between cuts to keep the frosting lines distinct.

Choosing Sprinkles for the Batter

Use rainbow jimmies intended for baking rather than nonpareils. Nonpareils and some other sprinkles can release color into wet batter, leaving streaks instead of distinct flecks. Even with jimmies, colors can behave differently by brand, so fold them in gently just before dividing the batter.

Cooling and Frosting the Layers

Check that each layer is cool through the center before stacking; warmth can soften the buttercream and make the cake slide. Keep the filling layers even so the three cake layers and white frosting lines show clearly in each slice. A thin crumb coat catches loose crumbs before the final exterior coat goes on.

Storing and Freezing the Cake

Keep the frosted cake covered. In a cool room, it can stay at room temperature for short-term serving; refrigerate it for longer storage, up to about five days. Let chilled slices sit toward room temperature before serving so the cake and buttercream soften.

For make-ahead layers, cool them completely, wrap them tightly, and freeze for up to about three months. Thaw them while still wrapped, then unwrap and frost. No reheating is needed.

Nutrition

Approximate nutrition per serving, based on 1/14 of the cake: 780 calories, 5g protein, 41g fat, and 97g carbohydrates. Approximate values per 100g: 435 calories, 3g protein, 23g fat, and 54g carbohydrates. Values vary with slice size and whether cream or milk is used in the frosting.