Ingredients1/2 cup butter1 1/2 cups white sugar1 egg1 teaspoon vanilla extract2 cups all-purpose flour1 teaspoon baking soda1/4 teaspoon salt1 cup buttermilk2 cups rhubarb, chopped1 tablespoon all-purpose flour1/4 cup butter2 teaspoons ground cinnamon1 cup packed brown sugarDirectionsIn a large bowl, cream together butter or margarine and sugar. Beat in egg and vanilla.In another bowl, sift together 2 cups flour, soda, and salt. Add sifted ingredients alternately with buttermilk to creamed mixture.Toss rhubarb with 1 tablespoon flour, and stir into batter. Spoon batter into buttered 9 x 13 inch pan, and smooth the surface.Blend together 1/4 cup butter or margarine, cinnamon, and brown sugar; sprinkle evenly over batter.Bake at 350 degrees F (175 degrees C) for 45 minutes.