Beat egg yolks in top of a double boiler until thick and lemon colored. Add 1/2 cup sugar and lemon juice; beat well. Cook over boiling water, stirring constantly, 10 minutes or until mixture thickens. Remove from heat; set aside to cool.
Beat egg whites (at room temperature) and salt until foamy. Gradually add remaining sugar, beating until stiff peaks form. Fold meringue into cooled egg yolk mixture. Fold whipped cream into meringue mixture.
Line bottom of a 2-cup metal ice tray (with divider removed) with 1/4 cup wafer crumbs. Pour prepared mixture over top, and sprinkle with remaining wafer crumbs; freeze until firm. Slice, and garnish each serving with a cherry half, if desired.