Preheat oven to 350°. Line baking pans with parchment and nonstick spray
In a large mixing bowl, stir together the flour, sugar, baking powder, and salt.
In a separate bowl, thoroughly whisk together the buttermilk, eggs, egg yolks, vanilla extract, and vegetable oil.
In the bowl with the dry ingredients, toss in the butter a few cubes at a time while beating thoroughly. Once all the butter is incorporated it should look like damp sand.
Gradually add in the liquid until the batter is fluffy and fully incorporated.
Split the batter evenly between your baking tins. Bake for 20-25 minutes or until a toothpick or cake tester comes out clean.
Let cool for 10 minutes before removing from the pan and let cool fully before frosting.