1/2 cup butter
3/4 cup white sugar
2 tablespoons grated orange zest
1 cup self-rising flour (1 cup self-raising flour substitute 1 cup all-purpose flour plus 1 tsp baking powder and 1/4 tsp baking soda.)
1/2 cup fresh orange juice
1 pinch salt
Preheat oven to 350 degrees F (175 degrees C).Grease one 8 inch round cake pan. Sift flour and set aside.
Cream butter, sugar and grated orange zest until light and fluffy. Beat in the egg yolks one at a time. Fold in sifted flour, alternating with orange juice.
In another bowl, whisk egg whites until stiff and add a pinch of salt. Fold whisked egg whites into the mixture. Spoon batter into prepared pan.
Bake in preheated oven for 35 to 40 minutes, or until a toothpick inserted into cake comes out clean.