Preheat Oven to 350˚F. Line bottoms of two 9″ cake pans with parchment paper (do not grease the sides).
How to Make this Sponge Cake:
Whisk egg yolks and vanilla, set aside.
Sift flour and baking soda, set aside
In the bowl of an electric stand mixer fitted with whisk attachment beat eggs whites on high speed. With the mixer on, add 1 cup sugar and continue beating 8-10 minutes until thick and fluffy, meringue until meringue forms soft peaks.
On the lowest speed of your mixer, add the egg yolk and vanilla mixture whisk,
Add flour and baking powder one tablespoon at a time. whisk on low speed or Fold with a spatula with each addition just until incorporated. Scrape spatula from the bottom to catch any pockets of flour and stop mixing when no streaks of flour remain. Do not over-mix or you will deflate the batter.
mix oil with 1 tablespoon of the batter and add it to the batter and fold
Bake at 350˚F for 35-40 minutes , or until top is golden brown. Remove from pan, transfer to a wire rack and remove parchment backing. Cool cakes to room temperature then slice layers equally in half with a serrated knife.