In the books it sounds luscious but there wasn't enough description to actually know what the heck it was.
And here, at last, it is!
Lemon Schaum Torte
Make Meringue Torte (below). Spread with cooled Lemon Torte Filling (below). Top with 1 cup whipping cream, stiffly whipped. Chill about 12 hr. before serving. 8 to 10 servings.
Meringue Torte: Heat oven to 275 degrees (slow). Beat 4 egg whites (1/2 cup) and 1/4 tsp. cream of tartar until frothy. Gradually beat in 1 cup sugar, a little at a time. Beat until very stiff and glossy. Tint, if desired, with food coloring. Spread on heavy brown paper on baking sheet in 8 or 9" round. Shape with back of spoon. Bake 60 min. Turn off oven and leave in until cool.
Lemon Torte Filling: Beat 4 egg yolks in small mixer bowl until thick and lemon-colored. Gradually beat in 1/2 cup sugar. Blend in 1/4 cup lemon juice and 2 tbsp. grated lemon rind. Cook over hot water, stirring constantly, until thick, 5 to 8 min. Cool.
