Old Fashioned Chocolate Cake

Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan. In a saucepan, melt 1 cup of butter. Stir in 1 cup water and 4 tablespoons cocoa powder. Remove from heat and set aside.
In a medium bowl, dissolve the baking soda in 1/2 cup of buttermilk. Stir in the eggs and vanilla. Mix in the cooled cocoa mixture.
In a large bowl, sift together the flour, sugar, cinnamon and salt. Make a well in the center and pour in the cocoa buttermilk mixture. Stir until blended. Pour batter into prepared pan. Bake in the preheated oven for 30 minutes, or until a toothpick inserted into the center of the cake comes out clean. Ice the cake with Buttermilk Pecan Icing while it's still warm.
For the icing: In a large saucepan, melt 1/2 cup butter with 4 tablespoons cocoa. Stir in 1/3 cup buttermilk, and heat until almost boiling. Stir in confectioners' sugar, vanilla, salt and pecans. Remove from heat. Mix well and pour over warm cake.