This One-Bowl Funfetti Birthday Cake is the most straightforward, reliable way to get a homemade birthday cake on the table without dragging out the stand mixer or dirtying every bowl in your kitchen. The method is built on a single mixing bowl and a whisk, which means less cleanup and fewer opportunities for error.
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The cake itself is a classic vanilla buttermilk cake, sturdy enough to stack and frost, but tender enough to melt on the tongue. The rainbow sprinkles are folded in at the very end to keep their colors from bleeding into the batter, and the frosting is a simple buttercream that pipes cleanly and holds its shape. You get a professional-looking result with home-kitchen simplicity.
I’ve tested this recipe with both natural and Dutch-processed cocoa variations, but the vanilla base is the star here. The buttermilk provides acidity that tenderizes the gluten and reacts with baking soda for lift, giving you a fine crumb and a domed top that’s easy to level. If you’re making this for a child’s party, the rainbow sprinkles are non-negotiable; for an adult twist, you can swap them for mini chocolate chips or chopped nuts.
Why You'll Love This Recipe
About the Ingredients
2 1/2 cups (315g) all-purpose flour
Provides structure. For a lighter crumb, you can replace 1/2 cup with cake flour, but all-purpose gives a sturdier cake that’s less likely to crumble when slicing.
2 1/2 teaspoons baking powder
Leavening agent that gives the cake lift. Make sure it’s fresh—if it doesn’t fizz when mixed with water, it’s past its prime.
1/2 teaspoon baking soda
Reacts with the buttermilk’s acid to help the cake rise and tenderize. There’s no substitute for baking soda here, so don’t skip it.
1 teaspoon salt
Enhances flavor and balances sweetness. Use fine sea salt, not coarse, to ensure even distribution.
1 3/4 cups (350g) granulated sugar
Sweetens and helps with browning. You can reduce to 1 1/2 cups if you prefer a less sweet cake, but don’t go lower or the texture may suffer.
3/4 cup (180ml) vegetable oil
Adds moisture and ensures a tender crumb. Canola or any neutral oil works; melted coconut oil also works but may add a slight coconut flavor.
3 large eggs, room temperature
Bind the batter and provide structure. Room-temperature eggs emulsify better, so take them out 30 minutes ahead or place them in warm water for 5 minutes.
1 cup (240ml) buttermilk, room temperature
Adds tang and activates the baking soda. If you don’t have buttermilk, add 1 tablespoon lemon juice to regular milk and let sit 5 minutes.
2 teaspoons vanilla extract
Pure vanilla is best; imitation works but has a harsher flavor. You can also scrape half a vanilla bean for extra specks.
1/2 cup (80g) rainbow jimmies sprinkles
The signature funfetti ingredient. Use jimmies (long, rod-shaped) not nonpareils (tiny balls) because they bleed less color and hold their shape better.
For the frosting: 1 cup (2 sticks, 226g) unsalted butter, softened
The base of the buttercream. Make sure it’s truly soft but not melted; if you can press a finger in easily, it’s ready.
For the frosting: 4 cups (480g) powdered sugar
Sweetens and thickens the frosting. Sift if it’s lumpy to avoid a gritty texture.
For the frosting: 2-3 tablespoons heavy cream or milk
Thins the frosting to spreadable consistency. Use as needed; heavy cream gives a richer mouthfeel.
For the frosting: 1 teaspoon vanilla extract
Flavors the frosting. You can also use almond extract for a different note, but then reduce to 1/2 teaspoon.
For the frosting: pinch of salt
Balances sweetness. Optional but recommended.
Tips & Tricks
- Make sure all wet ingredients (eggs, buttermilk) are at room temperature to ensure a smooth, emulsified batter—cold ingredients can cause curdling.
- Fold the sprinkles in gently with a spatula, not the mixer, to avoid breaking them and bleeding color into the white batter.
- Bake the cakes on the middle rack, and rotate the pans halfway through baking to ensure even browning.
- If you want a level cake, use a serrated knife to trim the domed tops after they’ve cooled completely.
Pro Tips
Step-by-Step Instructions
1. Preheat and Prep Pans
Preheat the oven to 350°F (175°C). Grease two 9-inch round cake pans and line the bottoms with parchment paper. This ensures the cakes release cleanly.
2. Whisk Dry Ingredients
In a large bowl, whisk together the flour, baking powder, baking soda, and salt until well combined. This distributes the leaveners evenly.
3. Add Wet Ingredients
Add the sugar, oil, eggs, buttermilk, and vanilla to the dry ingredients. Whisk until just combined—no more than 30 seconds. Overmixing develops gluten and makes the cake tough.
4. Fold in Sprinkles
Gently fold the sprinkles into the batter with a spatula until evenly distributed. Do not overmix; you want the sprinkles to stay intact.
5. Divide and Bake
Divide the batter evenly between the two prepared pans. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean and the top is golden brown. The cakes should spring back when lightly pressed.
6. Cool the Cakes
Let the cakes cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely. This prevents them from cracking.
7. Make the Frosting
In a large bowl, beat the softened butter with an electric mixer until creamy, about 2 minutes. Gradually add the powdered sugar, 1 cup at a time, beating on low speed. Add the vanilla, salt, and 2 tablespoons of cream, then beat on high for 2-3 minutes until fluffy. Add more cream if needed to reach spreadable consistency.
8. Assemble and Frost
Place one cake layer on a serving plate, spread a thick layer of frosting on top, then place the second layer. Apply a thin crumb coat, chill for 20 minutes, then apply the final coat. Decorate with extra sprinkles on top if desired.
Delicious Variations
Chocolate Funfetti
Replace 1/2 cup of the flour with 1/2 cup unsweetened cocoa powder and increase the buttermilk to 1 1/4 cups.
Lemon Blueberry
Add 1 tablespoon lemon zest and fold in 1 cup fresh blueberries instead of sprinkles. Use lemon extract in the frosting.
Confetti Cupcakes
Divide the batter into a 12-cup muffin tin lined with paper liners. Bake at 350°F (175°C) for 18-22 minutes, until a toothpick comes out clean.
How to Store One-Bowl Funfetti Birthday Cake
Refrigerator
Store frosted cake in an airtight container in the fridge for up to 5 days. Bring to room temperature before serving for best flavor.
Freezer
Wrap unfrosted layers tightly in plastic wrap and foil, freeze for up to 3 months. Thaw overnight in the fridge before frosting.
Reheating
For a warm slice, microwave for 10-15 seconds. Do not overheat or the frosting will melt.
Frequently Asked Questions
Q: Can I use oil instead of butter in this cake?
Yes, this recipe already uses oil instead of butter, which keeps the cake moist and tender. If you want to use butter, you can substitute melted butter for the oil, but the texture will be slightly denser.
Q: Why did my sprinkles bleed into the batter?
Sprinkles bleed when they are low quality or when you overmix the batter. Use high-quality jimmies and fold them in gently with a spatula just until distributed.
Q: Can I make this cake gluten-free?
Yes, you can substitute an all-purpose gluten-free flour blend that contains xanthan gum. The texture may be slightly more crumbly, so handle gently.
Q: How do I make a dairy-free version?
Use a plant-based buttermilk substitute (almond milk with lemon juice) and a dairy-free butter substitute for the frosting. The cake will still be moist and delicious.
Now that you have the blueprint for a perfect funfetti cake, go ahead and bake it for your next celebration. If you try it, leave a comment below or tag me on Instagram—I’d love to see your colorful creation. Keep your money moving.
One-Bowl Funfetti Birthday Cake
Easy Funfetti Birthday Cake: one bowl, no mixer, 45 minutes to a tender, colorful, party-ready layer cake with creamy vanilla frosting.
🧂 Ingredients
- 2 1/2 cups (315g) all-purpose flour
- 2 1/2 teaspoons baking powder
- 1/2 teaspoon baking soda
- 1 teaspoon salt
- 1 3/4 cups (350g) granulated sugar
- 3/4 cup (180ml) vegetable oil
- 3 large eggs, room temperature
- 1 cup (240ml) buttermilk, room temperature
- 2 teaspoons vanilla extract
- 1/2 cup (80g) rainbow jimmies sprinkles
- For the frosting: 1 cup (2 sticks, 226g) unsalted butter, softened
- For the frosting: 4 cups (480g) powdered sugar
- For the frosting: 2-3 tablespoons heavy cream or milk
- For the frosting: 1 teaspoon vanilla extract
- For the frosting: pinch of salt
📋 Instructions
- 1Preheat and Prep Pans — Preheat the oven to 350°F (175°C). Grease two 9-inch round cake pans and line the bottoms with parchment paper. This ensures the cakes release cleanly.
- 2Whisk Dry Ingredients — In a large bowl, whisk together the flour, baking powder, baking soda, and salt until well combined. This distributes the leaveners evenly.
- 3Add Wet Ingredients — Add the sugar, oil, eggs, buttermilk, and vanilla to the dry ingredients. Whisk until just combined—no more than 30 seconds. Overmixing develops gluten and makes the cake tough.
- 4Fold in Sprinkles — Gently fold the sprinkles into the batter with a spatula until evenly distributed. Do not overmix; you want the sprinkles to stay intact.
- 5Divide and Bake — Divide the batter evenly between the two prepared pans. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean and the top is golden brown. The cakes should spring back when lightly pressed.
- 6Cool the Cakes — Let the cakes cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely. This prevents them from cracking.
- 7Make the Frosting — In a large bowl, beat the softened butter with an electric mixer until creamy, about 2 minutes. Gradually add the powdered sugar, 1 cup at a time, beating on low speed. Add the vanilla, salt, and 2 tablespoons of cream, then beat on high for 2-3 minutes until fluffy. Add more cream if needed to reach spreadable consistency.
- 8Assemble and Frost — Place one cake layer on a serving plate, spread a thick layer of frosting on top, then place the second layer. Apply a thin crumb coat, chill for 20 minutes, then apply the final coat. Decorate with extra sprinkles on top if desired.
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