Preheat your oven to 325°F (165°C).
In a large mixing bowl, combine the cake flour, 1 cup of sugar, baking powder, and salt. Make a well in the center and add the oil, egg yolks, water, and vanilla extract. Beat until smooth.
In another large mixing bowl, beat the egg whites and cream of tartar until soft peaks form. Gradually add the remaining ½ cup of sugar, beating until stiff peaks form.
Gently fold the egg whites into the batter, being careful not to deflate the mixture.
Pour the batter into an ungreased 10-inch tube pan. Bake for 55-60 minutes, or until the cake springs back when lightly touched.
Invert the pan immediately and let the cake cool completely before removing from the pan.