In a microwave-safe bowl, combine the rhubarb, water and sugar. Microwave, uncovered, on high for 6-8 minutes or until rhubarb is tender, stirring occasionally. Stir in pudding mix until blended; cook for 30-90 seconds or until thickened, stirring occasionally. Serve over ice cream if desired.
If using frozen rhubarb, measure rhubarb while still frozen, then thaw completely. Drain in a colander, but do not press liquid out. This recipe was tested in a 1,100-watt microwave.