Preheat your oven to 325 degrees F. Spray three 6-inch round cake pans with non-stick spray. Line the bottoms with parchment paper and spray again. Set aside.
In a medium bowl, combined the cake flour, baking powder, salt and all of the seasonings. Whisk to combine the ingredients evenly. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium speed for about 3 minutes. Scrape down the sides and bottom of the bowl and mix again for another minute.
With the mixer on medium-low speed, add the eggs and egg yolks, one at a time. Make sure to mix well between each addition. Add the vanilla and stir to combine.
With the mixer on low speed, add 1/3 of the flour mixture to the sugar mixture. Stir for about 20 seconds and then add 1/2 of the buttermilk. Repeat the additions with another 1/3 of the flour mixture, the second half of the buttermilk and then the final 1/3 of the flour mixture. It's important to alternate adding these ingredients so they mix evenly, which will help your cake to rise more evenly. Only mix until the ingredients are incorporated. Over mixing your batter will cause it to be dense and/or sink in the oven.
Pour about 16 ounces of batter into each of the three 6-inch cake pans. Bake the cake layers on the middle rack in your oven for 35 to 40 minutes. Watch this cake closely at the end. Over baking your cakes will cause them to taste dry. When you insert a toothpick in the center of this cake, it should come out with a few moist crumbs on it.
Let the cakes cool in the pans for about 10 minutes, before inverting them onto cooling racks to cool completely. Once cooled completely, you can level the cakes and then wrap them in plastic wrap and freeze them until you're ready to stack and decorate the cake.