Method

Preheat an oven to 210°C.

In a bowl mix the butter, sugar and vanilla extract until combined.

Stir in the orange zest, flour and orange juice.

Add the egg to the mixture and then gradually the milk.

On an oven tray, place a large oven-proof dish with water. Place the bowl with batter into the dish filled with water (as a Bain-marie).

Bake for about 10 minutes.

Serve in small bowls or ramekins, with orange slices as an optional garnish.