Step 1

Preheat your oven to 325°F and spray two 8-inch round cake pans with cooking spray and line the bottoms with parchment paper and set aside. You can also bake this as a sheet cake in a 9x13-inch pan, there is no need to line the sheet pan.

Step 2

In a medium bowl, sift together the flour, baking soda, baking powder, and salt.4 Set aside.

Step 3

In a large bowl with a hand mixer or stand mixer fitted with a whisk attachment, cream together the sugar, oil, butter, and vanilla.

Step 4

Add the eggs and egg yolks one at a time beating after each addition just until combined.

Step 5

Using a rubber spatula, fold in the dry ingredients in 3 parts alternating with the buttermilk in 2 parts. Begin and end with the dry ingredients. Gently fold until only very small lumps remain. DO NOT use an electric mixer for this step.5

Step 6

Evenly divide the batter between the two prepared cake pans and bake for 30 to 35 minutes. OR add the batter to the prepared 9x13-inch pan6 and bake for 40 to 45 minutes. A toothpick should come clean from the center when done.

Step 7

Transfer the cake pans to a wire rack and allow the cakes to cool in the pan for 10 minutes before removing and allowing to cool completely (about 1 hour before frosting). Once cooled, frost and assemble the cake as desired. If making as a sheet cake, leave the cake in the pan and frost it.