in large mixing bowl, cream butter and sugar. add eggs, one at a time, beating well. beat in vanilla. combine dry ingred. add to creamed mixture alternately with buttermilk. stir in rhubarb. pour into 13x9x2 in. baking dish.

for topping....in small bowl, combine flour, brown sugar and Cinnamon cut in butter until mix looks like coarse crumbs. sprinkle over batter. bake at 350° for45-55 min. or until toothpick comes out clean. cool on wire rack