Butter and flour the pan, shake out the excess flour.
Preheat Oven
Preheat oven to 350F.
Flour Mixture
In a small bowl, whisk together all-purpose flour (3/4 cup, 100 grams), baking powder (1/2 teaspoon), and salt (1/8 teaspoon). Set aside
Meringue
In a clean bowl, on medium-high speed, beat two egg whites with cream of tartar until foamy, soft peaks are formed. Gradually beat in half of the granulated sugar (1/4 cup, 50 grams). Beat until stiff glossy peaks are formed
Egg Yolk Mixture-Ribbon Stage
In a mixing bowl, on medium-high speed, beat two egg yolks with remaining granulated sugar (1/4 cup, 50 grams) until pale in color and doubled in volume, about 3 minutes. Gradually beat in oil (2 tablespoons), decrease the speed to medium, and beat in warm water or milk (2 tablespoons), and Vanilla Extract (1/2 teaspoon). Scrape down the sides of the bowl, and beat for 20 more seconds.
Sponge Cake Batter
Alternating, in 3 additions, fold flour and meringue into the egg yolk mixture. Sift 1/3 of the flour mixture into the egg yolk mixture and fold it into the batter. Then add 1/3 of the meringue and again fold it in. Repeat until you have to flour and meringue left.
Bake Sponge Cake
Bake the cake at 350F for about 14 minutes, or until a toothpick inserted in the middle comes out clean.