Lemon Sponge Pudding - Ireland

In a large bowl with an electric mixer cream together 1/2 stick unsalted butter, softened, and 3/4 cup sugar, beat in 3 large egg yolks, 1 at a time, beating well after each addition, 1/3 cup each of lemon juice and all-purpose flour, 1 Tbsp grated lemon rind, and 1/4 tsp salt, and combine the mixture well. Add 1 1/2 cups milk in a stream, beating, and combine the mixture well. In a bowl beat 3 large egg whites with a pinch each of cream of tartar and salt until they hold stiff peaks. Stir one fourth of the whites into the lemon mixture, fold in the remaining whites gently but thoroughly, and transfer the mixture to a buttered  1 1/2-quart glass souffle dish. Set the dish in a deep pan, add enough boiling water to the pan to reach halfway up the sides of the dish, and bake the dessert in a preheated moderate oven (350 F.) for 50 minutes, or until it is puffed and the top is golden. Sift confectioners' sugar over the top and serve the dessert warm or chilled. (The sponge will separate, forming a custard-like sauce on the bottom. Spoon the top onto dessert plates and spoon some of the sauce over each serving.) Serves 4.