1 1/2 cups packed brown sugar
1/2 cup (1 stick) butter or margarine, softened
1 tsp vanilla
1 cup buttermilk
2 1/4 cups flour
1 tsp baking soda
3 generous cups chopped fresh rhubarb
1/3 cup packed brown sugar
1/2 cup chopped walnuts
1 tsp cinnamon
Cream together butter/margarine and brown sugar in a large bowl. Add egg and vanilla and mix well. In separate bowl, mix flour and baking soda. Gradually add flour mixture to egg mixture, alternating with buttermilk, stirring at low speed until very smooth and creamy. Stir in rhubarb. Let sit a minute or two for juices to come out of rhubarb. Stir again and pour into greased 9" x 13" pan.
For topping, mix all topping ingredients, stir well and sprinkle over cake batter. It should just cover the whole surface of the cake. Bake at 350 degrees about 50 - 60 minutes or until surface of cake is not shiny. A knife inserted in centre of cake will come out with cooked rhubarb on it but no uncooked batter.