Created by KittenCal on August 20, 2012
Step 1: Preheat oven to 350 degrees F. Position oven rack to second-lowest position. Grease a 13 x 9-inch baking dish.
Step 2: In a small bowl using fingers mix together the topping ingredients until crumbly; set aside.
Step 3: In a large bowl cream 1/2 cup butter with sugar until fluffy (about 2 minutes). Add in egg and vanilla; beat until well combined.
Step 4: In a small bowl mix together 2 cups flour with baking soda, salt and a pinch of nutmeg; add to the creamed mixture alternately with buttermilk.
Step 5: Toss the chopped rhubarb with 1 tablespoon flour then stir into the batter along with the walnuts.
Step 6: Sprinkle the prepared topping mixture evenly over the top of the batter.
Step 7: Bake for about 45-50 minutes. Serve cake warm with vanilla ice cream or whipped cream.