Funfetti cakes are all about joy, color, and celebration — and this full-size Funfetti Birthday Bento Cake brings all that excitement into a soft, fluffy, bakery-style cake. With rainbow sprinkles baked into every slice, a creamy vanilla buttercream, and a light, tender crumb, this cake is perfect for birthdays, celebrations, and everyday happiness.

Even though “bento cake” refers to a minimalist aesthetic, this recipe is written as a full-size 8-inch celebration cake, giving you plenty of space for fun piping, sprinkles, and decorations.

Ingredients (Full-Size 8-Inch Cake)

Dry Ingredients

• 2 ½ cups all-purpose flour
• 1 ½ cups granulated sugar
• 2 teaspoons baking powder
• ½ teaspoon baking soda
• ½ teaspoon fine salt

Wet Ingredients

• ½ cup unsalted butter, softened
• ½ cup vegetable oil
• 3 large eggs, room temperature
• 1 tablespoon vanilla extract
• 1 cup buttermilk, room temperature

Funfetti Add-Ins

• ¾ cup rainbow jimmies (sprinkles that do not melt easily)

Vanilla Buttercream Frosting

• 1 cup unsalted butter, softened
• 3 cups powdered sugar
• 2 tablespoons milk or heavy cream
• 1 tablespoon vanilla extract
• Pinch of salt
• Extra rainbow sprinkles for decorating

How to Make Funfetti Birthday Bento Cake?

1. Prepare Your Baking Pan

• Line an 8-inch round cake pan with parchment paper.
• Grease the sides lightly with butter or oil.
• Preheat the oven to 350°F (175°C).

2. Mix the Dry Ingredients

In a bowl, whisk together:

• flour
• baking powder
• baking soda
• salt

Set aside.

3. Make the Cake Batter

In a larger bowl:

1. Beat butter + sugar until light and creamy.
2. Add oil, mixing until fully combined.
3. Add eggs one at a time, mixing well.
4. Stir in vanilla extract.

4. Add Buttermilk and Dry Ingredients

Add the flour mixture in three parts, alternating with buttermilk.
Mix gently until just combined — do not overmix.

5. Fold in the Sprinkles

Use a spatula to fold in the rainbow sprinkles.
(Choose “jimmies,” not nonpareils, to prevent color bleeding.)

6. Bake the Cake

• Pour batter into the prepared pan.
• Bake 30–35 minutes or until the center springs back.
• Cool completely before frosting.

Frosting Your Funfetti Bento Cake

Make the Buttercream:

Beat butter until fluffy.
Add powdered sugar gradually.
Mix in vanilla, salt, and milk.
Beat until silky smooth.

Decorate the Cake (Bento Style)

• Apply a thin crumb coat.
• Chill for 15 minutes.
• Add a smooth final layer of buttercream.
• Keep the decoration minimalist — common bento designs include:
  * Smiley faces
  * Hearts
  * Short birthday messages
  * Cute piping borders

Top with extra rainbow sprinkles for a fun look.

Variations

1. Chocolate Funfetti Cake

Replace ½ cup flour with cocoa powder.

2. Strawberry Funfetti Cake

Add 1 teaspoon strawberry extract for fragrance.

3. Gluten-Free Funfetti Cake

Use a 1:1 gluten-free baking flour mix.

Common Mistakes to Avoid

• Using nonpareils sprinkles — they melt and discolor the batter.
• Overmixing — causes a dense cake.
• Cold eggs or buttermilk — affects rise.
• Overbaking — makes the cake dry.

Storing Your Funfetti Cake

• Room temperature: 2 days (covered)
• Refrigerator: 5 days
• Freezer: Up to 2 months (wrap slices individually)

Serving Ideas

• Serve with vanilla ice cream
• Add whipped cream
• Pair with fresh berries
• Drizzle with white chocolate

FAQs?

1. Can I use regular milk instead of buttermilk?

Yes — add 1 tablespoon vinegar to 1 cup milk.

2. Why did my sprinkles melt inside the cake?

You used nonpareils — choose rainbow jimmies.

3. Can I bake this as a layered cake?

Absolutely — divide into two 8-inch pans.

4. Can I color the batter?

Yes! Add food coloring for pastel or rainbow layers.

Conclusion

The Funfetti Birthday Bento Cake | Colorful Mini Cake Idea is the perfect blend of fun, color, and soft bakery-style texture. From the fluffy crumb to the creamy vanilla frosting, every bite brings joy and celebration. Whether it’s a birthday, holiday, or everyday treat, this cake always brings smiles.