Big Batch Confetti Cake With Buttercream

The kitchen still smells like vanilla and butter when I think about my daughters last birthday. She had very specific requests about the sprinkles needing to be everywhere, and I mean everywhere in the batter, on the frosting, even pressed into the sides. We ended up with rainbow flecks on the floor, in our hair, and somehow one found its way into my apron pocket where I discovered it days later.

Last summer I made this for a block party and watched a grown man literally do a little happy dance when he took his first bite. Someone asked for the recipe before they even finished their slice, and another person went back for seconds which is basically the highest compliment you can get at a potluck.

Ingredients

• All purpose flour: The structure that holds all those sprinkles in place, dont skip the measuring
• Granulated sugar: Sweetens and keeps the crumb tender, exactly 500 grams works perfectly here
• Baking powder and baking soda: The lift team that makes this cake fluffy instead of dense
• Fine sea salt: Balances sweetness and actually makes the vanilla flavor pop
• Whole milk: Room temperature milk blends better into the batter for even texture
• Vegetable oil: Keeps the cake moist for days, butter alone cant do this job
• Unsalted butter: Melted and slightly cooled adds flavor while oil keeps it tender
• Large eggs: Also room temperature so they emulsify properly into the batter
• Pure vanilla extract: Never skimp here, this is the main flavor profile
• Rainbow sprinkles: Use jimmies in the batter to prevent color bleeding into your cake
• Unsalted butter for frosting: Room temperature is non negotiable for smooth buttercream
• Powdered sugar: Sift it first or risk lumpy frosting every single time
• Milk for frosting: Adjusts the consistency to perfectly spreadable

Instructions

Get your oven ready:

Preheat to 350°F and line two 9x13 pans with parchment, greasing everything thoroughly so nothing sticks later

Whisk the dry team:

In a big bowl combine flour, sugar, baking powder, baking soda, and salt until everything looks evenly distributed

Mix the wet team:

In another bowl whisk together milk, oil, melted butter, eggs, and vanilla until completely smooth

Bring them together:

Pour wet into dry and mix just until combined, overmixing makes tough cake

Add the magic:

Fold in those rainbow jimmies gently, watch the colors dance through the batter

Bake it up:

Divide between pans and bake 30 to 35 minutes until a toothpick comes out clean

Cool completely:

Let them rest 10 minutes in pans then move to wire racks, warm cake melts buttercream into a sad puddle

Make the frosting:

Beat butter 2 minutes until creamy, then add powdered sugar gradually, followed by milk and vanilla

Fluff it up:

Beat on high 3 minutes until light and fluffy, this step is what makes it taste professional

Frost and decorate:

Spread thick layers on cooled cakes and shower with more sprinkles because more is more

Save

This recipe became my go to the year I accidentally volunteered to bring cake for every single classroom celebration. Now whenever I show up with those familiar parchment wrapped pans, people actually cheer before they even take a bite.

Making This For A Crowd

Two 9x13 pans serve 24 people generously, but I've learned to always make the full recipe even for smaller groups. The leftovers keep incredibly well and somehow taste even better on day two when the flavors have had time to settle in and get friendly with each other.

Frosting Like A Pro

The secret to bakery smooth buttercream is letting it mix longer than you think necessary. Those extra minutes on high speed whip in tiny air bubbles that transform grainy sugar butter into silky perfection, and suddenly your homemade cake looks like it cost forty dollars at a fancy bakery.

Sprinkle Science

Not all sprinkles are created equal, and I learned this the hard way when an entire batch turned into a muddy disappointment. Jimmies are coated and wont bleed, but those tiny round nonpareils will turn your batter gray and sad in the oven.

• Always save nonpareils for decorating the outside only
• Press sprinkles into the sides immediately after frosting before it forms a skin
• Extra sprinkles on the cutting edge make every slice look intentional and cheerful

Save

Every birthday deserves this kind of cake, the kind that makes people light up before they even take a bite. Hope it becomes your celebration tradition too.

Recipe FAQs

→ Can I make this cake in advance?

Yes, you can bake the layers up to 2 days ahead. Wrap cooled cakes tightly in plastic wrap and store at room temperature. Frost on the day of serving for best results. The frosted cake also refrigerates well for up to 3 days—bring to room temperature before serving.

→ Why use both oil and butter in the batter?

The combination gives you the best of both worlds: butter provides rich flavor while oil ensures extra moisture and tenderness. This dual approach creates a cake that stays fresh longer and develops a soft, velvety crumb that doesn't dry out quickly.

→ What's the difference between jimmies and nonpareils?

Jimmies are the elongated, soft sprinkles that hold their shape during baking. Nonpareils are tiny, round balls that can bleed color and create a speckled appearance. Always use jimmies in the batter for vibrant confetti dots without color bleeding.

→ Can I freeze the unfrosted cake layers?

Absolutely. Wrap cooled layers completely in plastic wrap, then foil, and freeze for up to 3 months. Thaw overnight at room temperature before frosting. The texture remains virtually identical to freshly baked.

→ How do I prevent my buttercream from curdling?

Ensure all ingredients are at room temperature before mixing. Add powdered sugar gradually, beating well after each addition. If the mixture looks curdled, keep beating—it will come together. The high-speed whipping stage is crucial for that silky, smooth texture.

→ Can I make this as a layer cake instead of sheet cakes?

Definitely. Divide the batter between three 9-inch round pans and reduce baking time to 25-30 minutes. You'll have a stunning triple-layer celebration cake perfect for more formal occasions. Adjust frosting quantity accordingly for stacking.