Sift together 1 cup flour, baking powder, and salt. Cut in 2 tablespoons butter or margarine. Add egg and milk; mix. Press mixture into a greased 9 inch pie plate.
Arrange rhubarb in pie shell. Sprinkle with dry gelatin mix.
Combine 1/2 cup flour, sugar, cinnamon, and melted butter or margarine; sprinkle on top of pie.
Bake 350 degrees F (175 degrees C) for 50 minutes, or until rhubarb is tender.