Add a little fun to your next dessert with this 6-inch Single Layer Funfetti Cake! It is moist, tender, and mixed with a handful of rainbow jimmies! For added vanilla flavor, pair it with this small-batch vanilla flour buttercream and top it with a mix of some of your favorite sprinkles! It's another easy and delicious single-layer cake recipe you'll be sure to love!

8 Reasons to Love This Funfetti Cake

1. It's easy to make.
2. Yields only 1, 6 inch single layer funfetti cake—but thick enough that it can be sliced into 2 layers!
3. Perfect for up to 4 people people (or really even up to 6—if no seconds is cool with everyone).
4. It's moist and tender—thanks to the added buttermilk!
5. Adding rainbow jimmies (or sprinkles) to your desserts is fun and makes people smile!
6. It's paired with a vanilla buttercream that is NOT made with powdered sugar.
7. It's wonderful for small dinner parties or birthdays, an intimate dinner, or a really nice way to treat yourself!
8. You can make your very own rainbow sprinkle mix for decoration!

Let's Talk Ingredients

To make these moist and tender vanilla funfetti cake, you'll need the following ingredients:

• Cake Flour
• Baking Powder
• Salt
• Unsalted Butter
• Granulated Sugar
• 1 Egg
• Vanilla Extract
• Buttermilk
• Rainbow Jimmies (or sprinkles) + plus more for decoration (see below)

Substitutions

Cake flour substitute. If you do not have or have difficulty finding cake flour in your area, you can use the substitute shown below.

Whole Milk. If you do not have buttermilk on hand, you can use whole milk. For a closer thickness to buttermilk, however, you can also use whole milk with 2 teaspoons of lemon juice. Add the lemon juice into the ⅓ measuring cup first, then fill the remaining cup with the whole milk. Pour it into a small glass bowl and let it sit for about 5 minutes to thicken.

I did not test this recipe using any alternative flours, egg substitutes, dairy free alternatives, or cake pans.

Homemade Cake Flour Substitute

If you don't keep cake flour on hand, fear not—you can make it at home! You only need all-purpose flour, cornstarch, and a sifter!

To make homemade cake flour:

1. Add 1 tablespoon of cornstarch to a ½ cup measuring cup.
2. Fill the remaining measuring cup with all-purpose flour.
3. Run the mixture through a sifter. Once is good, but twice is even better!

If you want to have a little more on hand, I recommend doubling the above recipe. Keep it stored in an airtight container either at room temperature or, my preference, the freezer.

What is Flour Buttercream?

Flour buttercream, also known as Ermine buttercream or boiled milk frosting, is frosting made without powdered sugar.

Its ingredients include all-purpose flour, granulated sugar, salt, milk, vanilla extract, and unsalted butter.

While the process is slightly more time consuming, the result gives you a less sweetened buttercream that is similar to swiss meringue, with the creaminess of the classic American buttercream frosting.

How to Make Small Batch Vanilla Flour Buttercream

This buttercream is made in two parts and will take some time.

If you prefer to make my small batch vanilla buttercream with powdered sugar, visit my Small Batch Vanilla Cupcakes recipe.

Step one. Mix your all-purpose flour, granulated sugar, and salt together with a whisk. Add in the milk and whisk once more.

Step two. Over low-medium heat bring the mixture to a near boil, continually stirring with a spatula. It's also a good idea to scrape the bottom of the saucepan too. Your mixture will begin to thicken to the consistency of paste and will have a wet, glossy look to it.

Step three. Turn off the heat and continue to stir and scrape for 1-2 minutes more. This will help release some of the heat as well as remove some of the shine.

Step four. Pour the mixture evenly onto a plate (preferably one with a lip or an edge) and immediately cover with plastic wrap, pressing it directly onto the mixture. This will keep the mixture from forming a skin. Let it cool to room temperature before continuing to the next step.

Step five. Before starting, make sure the butter is at room temperature and cut into cubes. Beat the butter using a stand mixer or a hand mixer for 2-3 minutes or until it's light in color and fluffy in texture.

Step six. Add it one spoonful at a time and not all at once. Let each spoonful mix into the frosting before adding the next spoonful. Once it's all been added, scrape down the sides of the bowl, add in the vanilla extract, and mix once more on medium-high speed.

You can make either the thickened flour mixture or the flour buttercream 3-5 days in advance. Keep it stored in the refrigerator, then bring to room temperature when ready to use.

For the vanilla flour buttercream, you should whisk it again with the mixer to bring it back to life.

Make Your Own Sprinkle Mix

If you want to mix things up a bit with the sprinkles you add to your 6 inch funfetti cake, here's a combination to try! Of course, the sky is the limit for the type of sprinkles you use as well as how many different combinations. For this mix, I used the following 3:

• Rainbow Jimmies (or Rainbow Sprinkles)
• Rainbow Nonpareils
• Rainbow Confetti Sprinkles

Note the kind that I used have a natural coloring to them and are not super bold and bright. They're more muted in color.

Add a small amount to a jar with a lid (a ball canning jar will work well), make sure the lid is on good and tight, then shake it up. Wah-la—your own sprinkle mix!

Single Layer Cake Troubleshooting / FAQs

More Single Layer Cakes!

Keep your love of the single layer cake going with any of these fabulous recipes!

• Chocolate Cake
• Red Velvet Cake
• Carrot Cake
• Chocolate Flourless Cake