Preheat your oven to 325°F (165°C).
In a large mixing bowl, combine the flour, sugar, baking powder, and salt.
Make a well in the center of the dry ingredients and add the egg yolks, oil, water, and vanilla extract. Mix until smooth.
In another bowl, beat the egg whites and cream of tartar until stiff peaks form.
Gently fold the egg whites into the batter until just combined.
Pour the batter into an ungreased 10-inch tube pan.
Bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean.
Invert the pan immediately and let the cake cool completely before removing from the pan.