Whisk egg yolks, sugar and grated orange rind until mixture turns light and fluffy. Beat in orange and lemon juices and stir in corn oil. Fold in sifted self-raising flour and corn flour.
In another bowl, whisk egg whites until frothy, then add cream of tartar, sugar and salt. Beat until fluffy and just stiff.
Fold egg yolk mixture into the egg white mixture and mix gently and evenly with a spatula.
Pour the mixture into an un-greased chiffon tube pan. Bake in preheated oven at 175180°C for 4045 minutes or until cake is lightly browned and firm to the touch. Remove cake from oven. Invert the cake pan immediately and leave undisturbed until completely cooled. To remove the cake from the pan, run a thin-bladed knife around the sides of the pan.