Cake Directions: Preheat oven to 350degrees. In a large bowl, combine flour, sugar, baking soda, and cinnamon. Set aside. Put butter, cocoa powder, Coca-Cola, and buttermilk in a saucepan over medium heat. Stir until it comes to a boil. Remove from heat and pour it into the flour mix. Stir until combined. Add 2 eggs and 1 tsp vanilla. Mix. Pour into greased 9x13. Bake for approximately 30 minutes. I like to take it out a little early so it is nice and moist.
Frosting Directions: Combine butter, cocoa powder, and remaining Coca-Cola in a saucepan (I use the same one I used for the cake) over medium heat until it comes to a boil. Remove from heat. Slowly whisk in powered sugar until smooth. Pour frosting over warm cake.
Recipe by Five Wooden Spoons at https://www.fivewoodenspoons.com/2013/05/27/lauras-coca-cola-cake/