1 1/2 c brown sugar  1/2 c shortning  1 egg  Beat till fluffy.   2 c flour  1 t soda  Sift together. Add 1/2 t salt and 1 c buttermilk, beat.   1 1/2 c finely cut rhubarb  1 t vanilla  Stir in.   Sprinkle on topping. Bake at 350 degrees for 35 minutes in greased and lightly floured pan.   Topping:  1/2 c sugar  1 t cinnimon.   Top with whipped topping.