Rhubarb Cake

1/2 cup oleo
1 1/2 cup brown sugar
1 egg
1 tsp. vanilla
1 cup buttermilk
2 cups flour
1/2 tsp. salt
1 tsp. baking soda
2 cups diced rhubarb added last

Topping
1/4 cup sugar
1 tsp. cinnamon
1/2 cup chopped walnuts

Sprinkle topping over batter and bake at 350 degrees for 40 to 50 minutes.