Preheat oven to 375°F (190°C).

Cream butter and sugar together until light and fluffy.

Beat egg yolks until thick and lemon colored.

Add the beaten egg yolks to the creamed butter and sugar.

Beat in fresh orange juice and grated orange zest.

Fold in flour.

Stir in milk until well combined.

In a separate bowl, beat egg whites until stiff peaks form.

Gently fold the beaten egg whites into the orange mixture.

Pour the batter into a greased 1 quart heavy baking dish.

Bake for 35 minutes, or until golden brown and set.

Let the cake cool slightly.

Refrigerate the cake until chilled before serving.