Step 1

Sift together both flours, baking soda, baking powder and salt. Set aside.

Step 2

Grease and flour 2 eight inch round cake pans and line the bottom with 2 circles of parchment paper.

Step 3

In the bowl of an electric mixer beat together the sugar, vegetable oil, butter and vanilla. Beat well at high speed with whisk attachment until light and fluffy

Step 4

Beat the eggs in one at a time, then beat in the 2 egg yolks.

Step 5

Fold in the dry ingredients alternately with the buttermilk.

Step 6

I always add dry ingredients in three divisions and liquid ingredients in 2 divisions. It is very important to begin and end the additions with the dry ingredients. Do not over mix the batter. As soon as it has no lumps in the batter, pour into the two prepared 8 inch cake pans.

Step 7

Bake at 325 degrees F for 30-35 minutes or until a wooden toothpick inserted in the center comes out clean. Allow the cake to cool in the pans for 10 minutes before turning out onto wire racks to cool completely.