TOSS rhubarb and strawberries with sugar in large saucepan. Stir in 2 Tbsp. water; cover. Cook on medium heat 5 min. or until rhubarb is desired tenderness, stirring occasionally. Remove from heat; cool slightly.
REFRIGERATE at least 2 hours.
PLACE 1 pound cake slice on each dessert plate when ready to serve. Top each cake slice with about 1/4 cup of the rhubarb mixture and about 2 Tbsp. of the whipped topping.