Because this cake cooks in a 9 X 13 pan, I always keep half out to use now and put the other half away for another day.
Preheat oven to 350 F degrees
Grease a 9×13-inch baking dish.
Combine flour, sugar, cinnamon, baking powder, and baking soda in a large bowl. Cut butter into flour mixture until mixture resembles coarse crumbs. Reserve about 1 cup of the crumb mixture.
Stir buttermilk, eggs, and vanilla into remaining crumbs until batter is just combined; pour batter into prepared baking dish. Sprinkle reserved butter crumbs over top of the cake batter.