Separate eggs, place egg yolks in one bowl and egg whites in another plus the extra egg white

Preheat oven to 170°c

In bowl place sifted flour, sugar (take 1/4 cup out), baking powder, salt. add orange zest and whisk until combined

Make well in the center and add the egg yolks, oil, orange juice, and vanilla essence. Beat until smooth

In separate bowl beat egg whites and beat until soft peaks form. gradually beat the 1/4 cup sugar and beat until stiff peaks form

With rubber spatula gently fold egg whites in 3 additions until just blended. Be careful not to deflate batter

Pour batter into greased pan

Bake for 55-60 minutes or until wooden skewer or knife inserted comes out clean

Butter cream icing. Add sugar and butter to bowl. Whisk with mixer until light and fluffy. Add milk and orange food color, whisk to combine well. Decorate cake