In a bowl add cake flour, sugar, baking powder and salt; stir. Use a spoon to make a well in the center of the flour. Place mashed bananas, oil, water, beaten yolks and vanilla into the well; use a spoon to mix until smooth. In a mixer add the whites; beat until they form peaks. Add the beaten egg whites to the banana mixture; fold them into the batter using the spoon. Pour the batter into a greased 10" tube pan or bundt pan.
2Bake 60-65 minutes. Test with a toothpick for doneness. Cool completely, then invert the cake onto a plate.