Preheat oven to 400 °
Spray or butter a 9x13” rectangular pan.

1. In a large bowl, combine the flour, sugar, and cinnamon. Set aside. 
   
   
2. In a medium saucepan, melt the butter. 
   
   
3. Add the cocoa and water and bring to a rapid boil. 
   
   
4. Remove from heat and pour over dry the ingredients, mixing well. 
   
   
5. Add the buttermilk, soda, vanilla, and eggs, mixing well.
   
   
6. Pour into the prepared pan and bake in top rack of the oven for 20–25 minutes.
   
   
7. While the cake is still warm, prick thoroughly with a fork and pour the frosting over the cake.
   
   
8. Cool before serving.
   
   
9. Refrigerate if desired. This cake tastes good both as a cool fudgy wedge taken straight from the fridge, or a decadent soft chocolate explosion at room temperature.