Cake:
Preheat oven to 400 degrees F. In a large bowl combine
the flour and sugar.
In
a small saucepan, or in a microwave dish, combine the
butter, cocoa and water. Heat to boiling. Pour over
the flour mixture and mix well.
Add
buttermilk, vanilla, cinnamon, salt, baking soda and
eggs. Mix well.
Pour
batter into a greased jelly roll pan. Bake for 20 minutes.
Icing:
5 minutes before the cake is done, combine butter, cocoa
and buttermilk in a medium saucepan. Bring to a boil.
Remove
from heat, beat in icing sugar and vanilla. Beat until
smooth. Remove cake from oven and spread icing while
the cake is hot.