Grease 2 pieces 5 inch cake pan or 1 piece 7 inch round cake pan. Preheat oven to 170 deg C.

Sift plain flour and baking powder together, add orange zest, mix well and set aside.

Beat butter, sugar and vanilla extract with an elecrtic mixer at medium speed until light and fluffy.

Use low speed and slowly add in beaten eggs until mixture incorporated, mix well.

Gradually add the sifted flour mixture, alternate with orange/lemon juice, stop machine.

Lastly add in natural yogurt, fold well with a rubber spatula.

Pour batter into cake pan and bake in preheated oven for about 30-35 minutes or until a cake tester inserted in cake comes out clean.

Remove cake from oven, let it stay in cake pan for 10 minutes. Then cool cake completely on wire rack.