Rainbow Cake

This week, I made a super cool rainbow cake for Alexandra, one of the other first years in the corporate department at work. But before I get to that, I want to make a quick plug for donations to my upcoming bike ride. I’ll be riding the Best Buddies Challenge ride on June 1, and I have until May 17 to reach my goal. If you want to learn more about the ride, you can check out my donation page here, or drop me a comment and I’m happy to chat about why you should consider donating. Thank you so much for any support you can provide!

But anyways, this cake. For each of my fellow first-years at work, I’ve promised to make some kind of baked good of their choosing for their birthday. Alexandra, months ago, asked if I could make this cake. It’s an explosion cake, so when you cut into it, sprinkles come cascading out. Of course I had to try.

Initially, I thought I’d just use Magnolia Bakery’s vanilla cake and vanilla buttercream recipes, which I’ve made cupcakes from in the past. But then, once I flipped a bit more through the cookbook, I realized there was a cake I hadn’t made yet: traditional vanilla birthday cake. Since it was Alexandra’s birthday, it seemed only fitting to use this as the base.

And then, since I was making a new cake, I thought I could try out a new icing as well. Enter creamy vanilla frosting. Unlike any frosting I’ve made before, and absolutely perfect for this cake. The only other thing I needed was to empty my entire collection of sprinkles inside and add some food coloring!

So first up, make the cake. Start by beating the butter on medium speed of a stand mixer fitted with the paddle attachment until smooth.

Add the sugar and beat until light and fluffy, about 3 minutes.

Beat in the eggs, one at a time, to incorporate.

In a separate bowl, whisk together the self-rising and all-purpose flours. Add to the batter in four additions, alternating with the milk and vanilla extract, but starting and ending with the flour. Beat after each addition.

Divide the batter between five bowls, and mix some food coloring gel into each. I went with pink, yellow, green, blue, and purple.

Now, to make a cute little cake, I used my 6-inch cake pans again. I have three, so I started by making three of the layers, and then made the final two. For each baking, I sprayed the pans with cooking spray and lined the bottom of the pans with parchment paper.

Bake at 350°F for about 20 minutes, until a toothpick comes out clean.

Allow to cool about 10 minutes in the pans before turning out onto a wire rack to cool completely.

While the cake layers are cooling, make the frosting. To do that, start by whisking the flour and milk together in a medium saucepan until smooth. Yes, you are making a roux for frosting. I told you this was unlike anything else I’ve made.

Heat over medium heat, stirring constantly, and cook until the mixture begins to bubble and is very thick. This will take 10-15 minutes, so be patient – you’ll think it’s getting thick, but if it’s only been 6 minutes, you’re wrong.

The whisk will cut through and leave a real trail. That’s when you’re ready to stop. When it gets that thick, remove it from the heat and place wax paper right on the surface of the mixture. Allow to cool for 30 minutes.

Once it’s cool, go back to your stand mixer and beat the butter on medium speed for 3 minutes, until creamy.

Add the sugar slowly, and beat continuously until light and fluffy, another three minutes.

Add the vanilla extract and beat to combine.

Finally, add in the cooled milk mixture, and beat on medium high speed for five minutes. It will lighten considerably in color.

Cover and refrigerate for exactly 15 minutes before using.

Now to assemble the cake! First, cut a circle out of the middle of the middle three layers (blue, green, and yellow if you’re following my color scheme). Save your cake circles for snacks later.

Next, put down the bottom layer (purple) and ice.

Add blue, and ice around the ring.

Repeat with green and yellow. Then, pour all the sprinkles you own into the center.

Finally, top with pink (which shouldn’t have a hole cut out) and frost the entire thing in white.

Refrigerate until ready to serve.

When you are ready to serve, either put the cake on something to capture the sprinkles, or really just lean into the mess you’re about to make. Alexandra chose the latter, and we ate cake for breakfast last Tuesday:

And despite the sprinkle-covered office, it tasted delicious!

So, even though this cake looks super impressive, I hope you’ll realize it’s actually not that bad. And if you really wanted to cut corners, you could make this pretty easily with boxed mix and store-bought frosting. But where’s the fun in that?

Enjoy!

Rainbow Cake

Ingredients:

Vanilla Birthday Cake

1 cup butter, room temperature
2 cups sugar
4 eggs
1 1/2 cups self-rising flour
1 1/4 cups all-purpose flour
1 cup milk
1 teaspoon vanilla extract

Creamy Vanilla Frosting

6 tablespoons all-purpose flour
2 cups milk
2 cups butter, room temperature
2 cups sugar
2 teaspoons vanilla extract

Directions:

Vanilla Birthday Cake

In a stand mixer fitted with the paddle attachment, beat butter on medium speed for about three minutes, until creamy.
Add sugar and beat for another three minutes, until light and fluffy.
Add eggs, one at a time, beating after each addition.
In a separate bowl, whisk together self-rising and all-purpose flours.
Add flour to batter in four additions, alternating with milk and vanilla extract, and beating well after each addition.
Separate batter into 5 bowls and color each with a different color of food coloring.
Bake each batch of batter in a 6-inch pan, sprayed with cooking spray and lined with parchment paper, at 350°F for 20 minutes, or until a toothpick comes out clean.
Allow to cool 10 minutes in pans before transferring to a wire rack to cool completely.

Creamy Vanilla Frosting

Start by whisking the flour and milk in a medium saucepan until smooth.
Put over medium heat, and cook, stirring constantly, until the mixture thickens and begins to bubble. This will take 10 to 15 minutes.
When thickened, remove from heat and press wax paper right into the surface. Cool for 30 minutes.
In a stand mixer fitted with the paddle attachment, beat butter on medium speed for 3 minutes, until fluffy.
Gradually add the sugar, beating until light and fluffy, another 3 minutes.
Add the vanilla extract and beat to combine.
Add the milk mixture and beat on medium high speed for 5 minutes, until frosting whitens considerably.
Refrigerate for exactly 15 minutes before using.

Assembly

Cut a circle out of the center of the three middle layers.
Place the bottom layer on a cake circle and ice.
Add the first “donut” layer and ice around the ring. Repeat with remaining two “donut” layers.
Pour the sprinkles into the center hole of the cake, filling the cake.
Place the final complete layer on the top. Ice the entire outside of the cake.
Refrigerate until ready to serve.

Rainbow Cake