Spray 9x13 pan with nonstick spray or use a nonstick dish.
Combine flour, sugar, salt and baking soda in mixing bowl.
In a small saucepan, heat the butter, cocoa, coke-cola, and buttermilk until boiling.
Pour over the dry mixture and mix thoroughly.
Add eggs and vanilla and mix well.
Pour into prepared 9x13 pan.
Bake for approximately 30 minutes. If a toothpick comes out clean the cake is done.
For FROSTING:
During the last 10 minutes of baking prepare the frosting.
In a small saucepan, combine butter, cocoa, and coke-cola. Whisk together and heat till boiling.
Remove from heat and slowly whisk in powdered sugar.
Remove cake from oven and slowly pour warm frosting over warm cake. Add chopped pecans on top if you desire. Allow cooling long enough for the frosting to set up before cutting.
Serve (with vanilla ice cream is great).
Notes
If you don't have buttermilk you can mix ½ cup milk and 1 teaspoon lemon juice.Allow it to set for 10 minutes (to thicken) and then mix with other ingredients just as you would the buttermilk.