For cake: Sift together the flour and sugar into a large bowl.
Combine the butter, cocoa and water in a saucepan; bring to a boil, stirring to dissolve the cocoa and melt the butter.
Add cocoa mixture to the flour mixture and mix well with a wooden spoon.
In a bowl combine the buttermilk, cinnamon, baking soda, eggs and vanilla; mixing well.
Add buttermilk mixture to the flour/cocoa mixture.
Beat until well blended (batter will be thin).
Pour into a greased and floured 13x9 baking pan and bake in a preheated 350 degree oven for 30 minutes or until cake tests done with a toothpick inserted in the center (if done the toothpick will come out clean).
Spread icing over hot cake in pan.
For icing: Combine the butter, cocoa and milk in a saucepan and bring to a boil; stirring until butter is melted and cocoa is dissolved.
Remove from heat and stir in vanilla and powdered sugar mixing well then add pecans and mix.