In 2-quart saucepan, cook rhubarb, granulated sugar and drink over medium heat 10 to 15 minutes, stirring occasionally, until rhubarb is tender and mixture is syrupy.
Add 1 cup of the strawberries; cook and stir 1 to 2 minutes, mashing slightly. Remove from heat. Stir in remaining strawberries. Cool slightly. Refrigerate at least 1 hour until chilled.
Just before serving, in medium bowl, beat whipping cream, powdered sugar and vanilla until stiff peaks form. In each of 8 parfait glasses, layer sauce, cake cubes and whipped cream; repeat layers. Serve immediately. If desired, garnish each serving with fresh strawberry slice.