Step 1

Preheat oven to 325 degrees. Line baking pan with parchment paper and/or spray well with nonstick cooking spray and set aside. (See notes)

Step 2

In a large bowl, whisk flour, baking powder, baking soda and salt together to combine. Set aside.

Step 3

In a liquid measuring cup, stir milk and vanilla together. Set aside.

Step 4

In a separate large bowl, mix butter, oil and sugar together until combined. Mix in eggs and egg whites, one at a time, until mixture becomes very light and fluffy. Scrape the sides of the bowl and mix again briefly.

Step 5

Alternate adding in flour mixture with milk mixture, being sure to start and end with flour. Scrape the sides and mix again to ensure a smooth batter. Divide evenly between baking pans and smooth the top. Bake 30-40 minutes in the lower 2/3rds of the oven. Cake will be done when a toothpick comes out clean or mostly clean with a few moist crumbs.

Step 6

Cool 15-20 minutes in cake pans before trying to invert on cooling racks. Cool completely before frosting and decorating.