This refreshing punch is cheering and unexpected, and gets such a pretty pink hue from the rhubarb. The base mix is sweet, but as the melting ice dilutes it, it achieves perfect balance.
Wash and trim rhubarb, and cut into ½-inch pieces. Cook in a heavy saucepan with 1 cup water and cinnamon over moderate heat, covered, 10 minutes.
Strain juices and discard rhubarb. Stir in sugar. Chill; add remaining lemon juice, pineapple juice, and water, and serve over ice.