Preheat the oven to 350℉. Line a 9X15 or 8X8 pan with parchment paper and set it aside.
Whisk all dry ingredients and set aside.
3½ cups All-purpose flour, 3 teaspoon Baking powder, 2 teaspoon Cornstarch, ½ cup Salt, 1½ cups Sugar
Whisk the egg white, sugar, and vanilla extract until smooth and milky.
¾ cup oil, 1 Egg white, 1 tablespoon Vanilla extract
Add this to the dry ingredients and whisk. The mixture will be thick.
Add the milk as small as ¼ cup and whisk well after each addition. The mixture will look lumpy, but it smooths out once you mix it well.
2 cups Milk
Pour the batter into the lined pan and bake for 30-35 minutes.
Let the cake cool down in the pan for 10 minutes, then transfer it to the cooling rack. Let the cake cool down completely before frosting it with American buttercream or your desired frosting.