2In a large bowl, beat the butter, Dr.Pepper and sugar together.
3Mix the cocoa, cinnamon, flour and baking soda; add to creamed mixture.
4Beat two eggs with the buttermilk and add to the bowl.
6For the topping,heat all 5 ingredients. Stir well until smooth.
7Remove cake from oven and pour topping onto cake. Let cake set for 30 minutes before serving.