1) To make egg yolk batter, combine egg yolks, salt, oil, banana puree, essence, sugar and coloring in a mixing bowl. Fold in flour and bicarbonate of soda until forms batter.
2) To make egg white foam, beat egg whites and cream of tartar until mixture forms soft peaks. Gradually add in sugar, beating at high speed until frothy and stiff peaks form.
3) Gently fold beaten egg white foam into egg yolk batter until blended.
4) Pour batter into ungreased 9-inch tube pan. Bake in preheated oven at 170 degrees C for 30-40 minutes or until cooked.