Funfetti Crumbs:

Preheat the oven to 300 F (150 C). Take a large baking sheet (no specific size necessary) and line it with parchment paper.

In the mixing bowl of your stand mixer, add in 1 cup of cake flour or AP flour (either works), 1/3 cup of granulated sugar, 2 tbsp light brown sugar, 3/4 tsp baking powder, 1/8 tsp table salt, and 2 tbsp of rainbow sprinkles. Fit your mixer with the paddle attachment, and mix these dry ingredients on low until they are well combined.

While continuing to mix on low, add in 1/3 cup of vegetable oil and 4 tsp of clear vanilla extract. Continue to mix on low until you see clusters forming. Some clusters will be larger and some will be smaller. Create about 14 to 15 very big clusters (about 3/4 to 1-inch diameter balls) with the palm of your hands. These will be for the top of the cake.

Transfer these clusters onto your prepared baking sheet and spread them evenly. Bake them into the preheated oven at 300 F (150 C) for 18 to 20 min, or until the clusters are lightly golden brown, stirring once or twice during that time to make sure the clusters bake evenly. They should still be moist to the touch, and will become crunchy as they cool.

Let them cool completely to room temperature. These can be made in advance and stored in an airtight container at room temperature for 1 week, or in the fridge or freezer for up to 1 month. Separate the 14-15 large clusters from the remaining smaller clusters.

Funfetti Cake Layers:

Preheat your oven to 350 F (175 C). Take a half sheet pan, which is 13" by 18", grease it with oil, butter, or nonstick spray, and line it with parchment paper.

Take a measuring cup, add in two-third cup of buttermilk, 1/2 cup of vegetable oil, and 1 tablespoon of clear vanilla extract. If clear vanilla extract is not available, you can use regular vanilla extract. Mix this together and set aside.

In a medium bowl, add in 2.5 cups of cake flour, 2 tsp of baking powder, 1/4 tsp of table salt, and 1/3 cup of rainbow sprinkles. Whisk this together to combine, and set this aside.

In the mixing bowl of your stand mixer, add in 1 cup granulated sugar, 1/4 cup light brown sugar, 1/2 cup vegetable shortening, and 6 tbsp unsalted butter at room temperature. Fit your mixer with the paddle attachment. If you have one with the flexible edge, that would be good here, so you won't need to scrape down the ingredients from the side of your bowl. If you just have a regular paddle attachment, make sure to scrape down the bowl occasionally. Mix the sugar with the fats on medium-high speed for 2 to 3 minutes, until they look light and fluffy.

Add in 4 room temperature eggs, 1 egg at a time, so that the previous egg is fully incorporated before adding in the next one. Then continue mixing at medium-high speed for another 2 to 3 minutes.

Turn the speed down to low, and very slowly pour in the buttermilk mixture. When all of the buttermilk mixture has been added, increase the speed back to medium-high, and continue to beat for another 4 to 6 minutes, or until the mixture has nearly doubled in size and looks smooth.

When the batter looks light, airy, pale-yellow, and you no longer see any unmixed streaks, turn the speed back down to low, and slowly add in the flour mixture. When all the dry ingredients have been added, continue to mix just until the batter comes together, about 1 minute or so.

Scrape down the sides if you need to, then spread this cake
batter into an even layer in the prepared 13" x 18" sheet pan,
smoothening it out as much as possible with your spatula. Then evenly add 2 tbsp of additional rainbow sprinkles on top of the batter. Bake this in the preheated oven at 350 F (175 C) for 28 to 30 minutes, or until the cake looks light golden brown, and the top surface springs back when gently pressed.

Place the pan on a wire rack and let it cool completely to room temperature. Once the cake has cooled to room temperature, it can be used for assembly, or can be wrapped in plastic and stored in the fridge for up to 5 days.

White Frosting:

In the bowl of your stand mixer, add in 16 tbsp, which is 2 sticks of room temperature unsalted butter, 1/2 cup of vegetable shortening, and 4 oz which is half a bar of cream cheese. Once again, fit your mixer with the paddle attachment with a flexible edge, and mix on medium-high speed for 2 to 3 minutes, until the mixture is smooth and fluffy.

Turn the speed down to lowest speed, and slowly add in 2 tbsp of light corn syrup and 2 tbsp of clear vanilla extract. Increase the speed back to medium-high, and beat for 2 to 3 minutes, until the mixture looks silky smooth and glossy white. Scrape down the sides of your bowl if necessary.

Turn down to low speed, and add in 2 cups of powdered sugar, 1/2 tsp table salt, 1/4 tsp baking powder, and 1/4 tsp of lemon juice. The acidity of the lemon juice will balance out the sweetness of the frosting. Once the ingredients look incorporated, increase the speed back to medium-high and continue beating for 2 to 3 minutes, until the frosting is completely smooth.

Use frosting immediately, or store in an airtight container in the fridge for up to 1 week. Bring to room temperature before using it on the cake.

Cake Soak:

Whisk together 1/3 cup of milk and 1 tsp clear vanilla extract.

Assembling the Cake:

Once the cake has cooled to room temperature, place a large rectangular piece of parchment paper bigger than the 13" x 18" cake on a smooth clean surface. Invert the cake onto it, carefully lift off the sheet pan, and peel off the parchment paper the cake was baked with.

Take an 8-inch cake ring, and press it into the bottom right corner of your cake, twisting it to make your 1st full 8" cake round. Then along the opposite top edge of the cake and as close to the first circle as possible, press the cake ring in again, twisting it to make your 2nd full 8" cake round. These 2 full rounds will be the top two out of 3 layers of cake.

Then wherever there's the most leftover cake - in this case it would be along the top edge above the 1st round, then another along the bottom edge below the 2nd cake round, use the ring to make partial cake rounds as big as possible. These partial
cake rounds plus the remaining scraps will be pieced together to make your 3rd cake round, which will be the bottom layer of cake.

Take whatever cake board or cake stand you'd like to serve your
cake on. Clean your 8" cake ring, make sure it's dry, and place it in the center of the cake board / cake stand.

Take a piece of acetate sheet that's 4 inches high, and cut it about 26 inches long. Using the metal cake ring as an outer shell, create a circle with the 4" high acetate sheet so that it's the same circumference as the metal ring, on the inside of the cake ring. 4" high acetate sheet will support the height of the finished cake.

Take the 2 partial cake rounds, and place them together in the ring to form the opposite sides of the bottom layer of cake. Then use the leftover scraps of cake to fill in the gaps between the partial rounds, or any uneven spaces, so that the bottom layer is as flat and circular as possible.

Using a pastry brush, generously moisten this base layer with 1/3 of the cake soak mixture.

Using the back of a small spoon, spread 1/4 cup of the frosting in an even layer on top of the first layer of cake. Make sure you get it all the way to the edges touching the acetate sheet, moving in a figure-eight or circular motion to make it as flat and even as possible.

Saving the 14-15 larger funfetti balls for the top, sprinkle 1/2 of the smaller funfetti crumbs evenly over the top of the frosting. Use the back of your spoon to press them gently into the frosting so they don't move. Then like before, use the back of a small spoon to spread another 1/4 cup of the frosting as evenly as possible over the crumbs, again making sure to get it all the way to the edges touching the acetate sheet.

Take one of the full cake rounds and place on top as the second layer of cake. Gently tap it down with the back of your hand to make sure the layers are snug. This will make the layers look good with no awkward gaps in between.

Then again, brush another one-third of the cake soak into this 2nd layer of cake. Like before, spread 1/4 cup of the frosting over the cake, sprinkle the second 1/2 of the smaller funfetti crumbs evenly over the top of the frosting, and then spread another 1/4 cup of the frosting of the crumbs - making sure spread them all the way to the sides touching the acetate sheet.

Then take the last full cake round and place it on top, as the third and final layer of cake. Gently tap it down like before. Then add the remaining frosting on top, and smoothen it out as flat and evenly as possible. Finally, garnish the frosting with the 14-15 large funfetti balls, either in a circle about half an inch from the edge, a mound in the center, or in whatever pattern you'd like.

Place your cake in the freezer for a minimum of 3 hours, or in the fridge overnight (minimum 12 hours) for the cake to set. If you're using the freezer, transfer it into the fridge for at least 3 hours before serving so that it softens up a bit. Keep it in the fridge till you're ready to serve it.

When you're ready to serve it, carefully slip the metal cake ring off, and slowly peel off the acetate sheets, exposing all the layers of this beautiful funfetti naked layer cake. Serve immediately. Enjoy!

The cake will keep in the fridge for up to 5 days or in the freezer up to 2 weeks. Since there's no frosting on the sides, once the acetate sheet is removed, for the leftovers, the sides of the cake and any exposed (non-frosted) surfaces should be wrapped with plastic to prevent the cake from drying out.