Funfetti Cake
New: September 2022

This is a half recipe for 3x 6" cakes. Original full is for 3x 9" cakes.
Cook Time: 28-30 minutes

Ingredients

CAKE

1.5 + 1/4 + 1/8 cups (222g) cake flour
1/2 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt (or no salt if using sales butter)
1/2 and 1/8 cups (1 stick + 2 TBS; 145g) unsalted butter, softened to room temperature
1/1 + 1/4 + 1/3 cups (175g) granulated sugar
1/6 cup (40 ml) vegetable oil
2 large eggs, at room temperature
1 large egg white, at room temperature
1.5 teaspoons (7 ml) pure vanilla extract
3/4 cups (190 ml) milk, at room temperature + 1 TBS of vinegar
3/8 cup (70 g) rainbow sprinkles (suggestion: betty crocker parlor perfect jimmies (NOT nonpareils)

VANILLA BUTTERCREAM
3/4 cups (1.5 sticks; 170g) unsalted butter, softened to room temperature
2/75 cups (325g) confectioners’ sugar
1/6 cup (40ml) heavy cream, at room temperature
1.5 teaspoons (7ml) pure vanilla extract (or use clear imitation vanilla extract for stark white frosting)
1/16 teaspoon salt
Additional sprinkles into frosting after frosting layers
Instructions

1. Preheat oven to 350°F (177°C). Butter and flour three 6-inch cake pans, line with parchment paper rounds, then grease the parchment paper. Suggestion: fit with wet cake strips.
2. Whisk the cake flour, baking powder, baking soda, and salt together in a large bowl. Set aside.
3. Using KitchenAid with a paddle attachment, beat the butter and sugar together on high speed for 5 minutes until completely creamed together and fluffy. 
4. Add vinegar to milk to make butter milk and stir.
5. Add the oil and beat for 1 minute until combined. 
6. Add the eggs, egg whites, and vanilla extract and beat on medium-high speed until combined.
7. Add dry ingredients and buttermilk in three additions, mixing after each addition just until incorporated. Do not over-mix this batter. The batter will be velvety and thick. 
8. Gently fold in the sprinkles. 
9. Pour and spread the batter evenly into each cake pan.
10. Bake for around 28–30 minutes or until the cakes are baked through. Tent the cakes with foil after about 15 minutes to prevent the sides and top from over-browning. To test for doneness, insert a toothpick into the center of the cake. If it comes out clean, it’s done.
11. Allow cakes to cool in the pans set on a wire rack for 20 minutes. Run a knife around the edges and then remove cakes from pans. Place cakes directly on wire racks to cool completely. The cakes must be completely cool before frosting and assembling.


Make the frosting: 
1. In a large bowl using a stand mixer fitted with a whisk or paddle attachment, beat the butter on medium speed until creamy, about 2 minutes. 
2. Add confectioners’ sugar, cream, vanilla extract, and salt. Beat on low speed for 30 seconds and then switch to high speed and beat for 2 minutes.  Add more confectioners’ sugar if frosting seems too thin; more cream if frosting is too thick; or an extra pinch of salt if frosting is too sweet.

Assemble cake + apply crumb coat: 
1. First, using a large serrated knife, slice a thin layer off the tops of the cakes to create a flat surface. Or use the cake slicer thing.
2. Place one cake layer on your cake stand or serving plate. Using a large icing spatula or small offset spatula, evenly cover the top with about 0.5 cup (about 125g) of frosting. Repeat with second cake layer, 0.5  more cup of frosting, and then the top cake layer. Spread a thin layer of frosting on the top and around the sides as a crumb coat. Run a bench scraper around the cake to smooth out crumb coat. 
3. Chill uncovered in the refrigerator for at least 30 minutes and up to 3 hours to set the crumb coat.
4. Mix sprinkles in frosting. Spread the remaining frosting all over the top and sides. Garnish with extra sprinkles, if desired.
5. Serve cake immediately, or if you need to store it for a few hours, place it in a cake carrier at room temperature for up to 4 hours. For longer storage, refrigerate covered cake for up to 1 day. Cake is best served at room temperature, though, so if it’s been refrigerated, let it sit out at room temperature for 30 minutes before serving.
Cover leftover cake tightly and store it in the refrigerator for 5 days.
Notes
Make Ahead & Freezing Instructions: The cake layers can be baked, cooled, and covered tightly at room temperature overnight. Likewise, the frosting can be prepared and then covered and refrigerated overnight. When ready to decorate, let the frosting sit at room temperature to slightly soften for 15 minutes, then give it one more mix with the mixer on medium speed for about 1 minute before frosting cake. (Add a splash of cream to thin out frosting if needed.) See step 10 if you want to store the frosted/decorated cake before serving it. Frosted cake or unfrosted cake layers can be frozen for up to 2–3 months. Thaw overnight in the refrigerator and bring to room temperature before decorating/serving. See how to freeze cakes for detailed instructions.

Eggs: 2 whole eggs provide structure, moisture, and richness. 1 extra egg whites keep the cake light. I don’t recommend using 3 whole eggs as a replacement; stick to the 2 eggs + 1 egg whites combination.
Buttermilk: If you don’t have buttermilk, you can make a DIY sour milk substitute. Add 1 Tablespoon of white vinegar or lemon juice to a liquid measuring cup. Then add enough whole milk to the same measuring cup until it reaches 1 and 1/2 cups. (In a pinch, lower-fat or nondairy milks work for this soured milk, but the cake won’t taste as moist or rich.) Stir it around and let sit for 5 minutes. The homemade “buttermilk” will be somewhat curdled and ready to use in the recipe.
Sprinkles: Avoid using sprinkles that will dye your batter. Steer clear from nonpareils, which are the little balls. The pictured cake uses Betty Crocker “Parlor Perfect” rainbow sprinkles, which I find in my regular grocery store. I also like to use these rainbow jimmies or pastel colored quins. Note that naturally colored sprinkles may lose their color in cake batter.
Originally from: https://sallysbakingaddiction.com/funfetti-layer-cake/

HEARD that this one is better:

https://mynameisyeh.com/mynameisyeh/2014/9/funfetti-cake