In a greased glass (don't use aluminum, rhubarb and aluminum don't get along)9 x 13 pan
Lay the rhubarb and sugar in the pan.
Over the rhubarb and sugar layer, sprinkle the cake mix.
Melt 1 1/2 stick of butter & drizzle over the dry cake mix.
Bake at 350 for 40 minutes or until golden & crispy on top.