Sift flour, sugar, baking powder, and salt 3 times in med. Bowl. Make a well. Then add in the following order oil, egg yolks, bananas, and vanilla. Beat until smooth. In large bowl beat egg whites until foamy. Add cream of tartar. Beat until form very stiff peaks. Over whites drizzle ¼ batter carefully fold it in repeat 3 times more. Bake 30-35 min. 350 degrees.