Preheat oven to 375 °. Cream butter. Add sugar and beat well. Beat egg yolks until thick and lemon colored. Add to creamed butter mixture. Beat in orange juice and zest. Fold in flour and stir in milk. Beat egg whites until stiff. Fold into orange mixture. Pour into a greased 1 quart heavy baking dish. Bake for 35 minutes. Let cool. Refrigete until chilled before serving.
