In a mixing bowl, combine the diced rhubarb, flour, sugar, milk, melted butter, baking powder, and vanilla extract. Mix until well combined.
Pour the mixture into a greased baking dish and spread evenly.
In a saucepan, mix the powdered sugar, cornstarch, and water. Bring to a boil and stir until thickened. Pour this sauce over the pudding in the baking dish.
Bake for 30 minutes or until the top is golden brown.
Allow to cool slightly before serving.
Notes
Serve warm with ice cream or whipped cream for added flavor.