eparate the egg yolks and whites into separate bowls. Preheat oven to 350F (180 C).
In a large mixing bowl, cream the butter and sugar together.
Add the egg yolks with this and keep mixing till it becomes a smooth cream.
Mix in the orange zest and the all purpose flour with this. Almost instantly you can smell the orange flavour in the cake mixture.
Add the orange juice, food colour and milk with this. The whole mixture will be thinner than the usual cake batter but thicker than pudding mixture. That's the perfect consistency for a pudding cake.
Now take a separate bowl and beat the egg whites till it forms peaks.
Fold this into the cake batter. Do this very gently so that egg whites are well combined but the foam does not go away.
Pour this mixture into a greased baking dish.
Fill a bigger baking dish with about 1 inch of hot water (water bath). Place the smaller dish filled with the batter into this bigger dish.
Transfer this (bigger dish with the smaller cake dish) together into the oven and bake for about 45 minutes. (NOTE: Each ovens are different. The cake may take 5-10 minutes more or less than the time specified. )
The cake should be completely set and not be runny.
Serve this as a warm dessert with some cold ice cream. If not chill it in the refrigerator and serve cold.