Makes four 6" layers
Preheat oven to 350 F. Line cake pans with parchment paper or coat generously with nonstick cooking spray.
Whisk together dry ingredients and set aside. In separate bowl, whisk together buttermilk and extracts; set aside.
Cream butter and sugar in mixing bowl until well blended, about 5 minutes. Add eggs, one at a time, incorporating well between each addition. Alternately add flour and buttermilk mixture, beginning and ending with dry ingredients. Stir in zest.
Pour 1/4 batter into one pan. Add a few drops of food coloring to batter and stir to distribute evenly. Pour about 1/3 of remaining batter in second pan. Add a few more drops of food coloring and stir to distribute. Pour half in next pan. Add another squirt of food coloring and stir. Pour remaining batter in last pan.
Bake for 25-30 minutes until center springs back when lightly touched. Allow to cool completely before frosting.
Vanilla Swiss Meringue Buttercream
Makes about 8 cups
You're going to need a double boiler for this recipe, but if you don't have one, don't worry! I don't either. We'll use our makeshift double boilers together. All you need is a pot filled with about 2 or 3 cups of water, and a heat safe bowl (like ceramic, glass or metal) that sits comfortably on top of your pot. You don't want the bowl to sit too deep and touch the water or you'll cook your eggs and that's just nasty in meringue. Ew.
So, now that you have your set up ready...
In bowl (not on the heat yet), whisk together egg whites and sugar until well combined. And before you have a cow from the fact that we're using egg whites here, yes, I mean you, Dad and Mama, use a candy thermometer to make sure your mixture reaches 160 F and you'll be fine.
Anyway, when water is simmering, place bowl on pot/double boiler and heat, whisking continuously, until the sugar melts completely. Test this by rubbing a little bit of the mixture between your fingers and feeling for any grittiness. If it's still gritty, keep heating.
Once smooth, remove from double boiler and whisk in salt. Pour mixture into bowl of stand mixer and mix on high speed with whisk attachment. If you don't have a stand mixer, a handheld is no problem. I just get bored standing around holding a mixer. Once the mixture comes to room temperature, about 10-15 minutes, you'll have a beautiful meringue that you can eat just as is, but we're making this into a buttercream, so press on!
Change to paddle attachment, if you have one, and add butter to the meringue, about 2 Tablespoons at a time. Make sure each chunk is fully incorporated before adding the next bit. Continue adding butter until all chunks are fully incorporated and mixture is smooth and creamy.
At this point, you may be getting nervous because your buttercream is looking a little strange, but don't give up! If it's runny or soupy...stick the whole bowl in the fridge for about 10-15 minutes to firm up and then continue whipping. If it's curdled and sick...just keep mixing! It will smooth out and look delicious again.
Once the buttercream is nice and smooth, add extract and mix to combine.
Center the yellowest layer on your cake plate and frost top with a thin layer of buttercream. Continue adding layers and buttercream until fully stacked. Frost sides of cake. Add copious amounts of sprinkles on top, adding extra as necessary.