Preheat oven to 350°F. Prepare 10-inch ungreased tube pan.
Sift together the flour, sugar, baking powder and salt in a bowl.
Make a well at the center and add oil, egg yolks, water and vanilla. Beat until smooth and no lumps occur. Set aside.
Using a stand mixer or electric hand mixer, beat egg whites until frothy. Add the cream of tartar. Continue to beat on high until soft peaks begin to form. Add sugar very gradually and continuously beating until meringue is glossy and stiff.
Gently fold the egg yolk mixture into the meringue until well blended, ensuring that you scrap the bottom of the bowl as you fold.
Pour into prepared ungreased tube pan.
Bake until golden and middle springs back when touched for about 45 minutes.
Invert onto the neck of a bottle.
Cool completely upside down.