Rhubarb Pudding Cake

1 lb fresh rhubarb, cut up (3 cups)
1 C granulated sugar
1 small box regular vanilla pudding mix
2 C milk
1 (1-layer size) yellow cake mix
Sifted confectioners' sugar
Few drops red food coloring

Heat oven to 350 degrees.  Combine rhubarb, granulated sugar, and red food coloring; let stand.  Prepare pudding mix according to package directions, using the two cups milk, Pour into a 9-inch square baking dish.  Top with rhubarb-sugar mixture.  Prepare cake mix according to package directions; spoon evenly over rhubarb.  Bake for 50 minutes or until cake is done.  Sprinkle with confectioners' sugar.  Serve warm.