Preheat the oven to 190°C (375°F) (gas 5)
Cream the butter, sugar, and orange zest together until light and fluffy. Then beat in the egg yolks. Next fold in the flour and cinnamon.
Stir in the milk and orange juice until well combined. The mixture will tend to curdle at this stage but don’t be concerned.
Whisk the egg whites until just before they reach the soft peak stage, then gently fold into the mixture.
Put to one side while preparing the apples.
Peel the apples and core with an apple corer to keep them whole. Then thinly slice crossways and layer them in the baking dish in circles.
Now pour the pudding mixture over the apples.
Place the dish on a baking tray and bake above the centre of the oven for about 40 minutes until the top is set and golden in colour.
Dredge with icing/powdered sugar just before serving.