Make the cake according to box directions.
Pour the cake mixture into a greased 9x13 pan.
Mix 4 cups of diced rhubarb with 2 cups white sugar.
Spoon the rhubarb and sugar mixture over the top of the cake mixture.
Pour 2 cups of cream over the top.
Bake in a preheated 350° oven for 45 minutes.
Allow to cool.
Serve with whipped cream or ice cream.
