Preheat oven to 325F.
Sift the flour, sugar, baking powder, and salt into a bowl. Make a well and add the egg yolks, vegetable oil, water, and vanilla. Set aside.
In a large bowl, beat the egg whites until foamy. Add in the cream of tartar and continue beating until stiff peaks form. Set aside.
Using the same beaters, beat the egg yolk batter. Scrape the bowl as needed. Beat until combined and smooth.
Fold in 1/4 of the egg whites into the egg yolk batter to lighten it up. Then gently fold in the rest of the egg whites in two equal parts until no white streaks remain.
Pour into an ungreased 10″ tube pan with removable bottom. Bake for 55-60 minutes or until a toothpick inserted into the center comes out clean. The top should be golden brown and spring back when lightly pressed.
Let cool completely upside down. Unmold and serve. Slice using a serrated knife.