Preheat oven to 350 degrees F (175 degrees C). Grease a 9×13 inch baking pan.
Combine flour and sugar in a large mixing bowl. In a medium saucepan, over medium heat, bring margarine, cocoa and water to a fast boil. Pour over flour mixture and mix well. Mix buttermilk, eggs, baking soda, cinnamon and vanilla into the flour mixture; mixing well after each addition. spread evenly into the prepared pan.
Bake for 35 minutes in the preheated oven, or until brownies begin to pull away from the sides of the pan.