Butter an 8 x 12-inch Pyrex dish. Break up cake and spread 1 inch thick on bottom of dish. Soak 1 tablespoon gelatin in 1/4 cup cold water. Using double boiler, beat 4 egg yolks well. Add 1/2 cup sugar, lemon juice, crushed pineapple and a pinch of salt. Mix and cook until thickens and coats spoon. Add gelatin; mix well. Let cool. Beat egg whites. Gradually add 1/2 cup sugar. Fold into cooled mixture. Pour this mixture over cake. Place in refrigerator overnight. Serve with whipped cream, nuts and cherry.