In a separate bowl combine melted butter, cocoa and water. Add to sugar and flour.
In a separate bowl combine soda, vanilla, buttermilk, and eggs. Add to previous mixture.
Bake on a bakers cookie sheet that has been sprayed with non-stick spray at 350 degrees for 15 -20 minutes until cake is firm.
Prepare the frosting while cake is in the oven. Combine all ingredients together and stir until smooth. Poor warm frosting over over slightly cooled cake.
Recipe by Table for Fifty at https://tableforfifty.com/gramma-cokes-chocolate-cake/