Grease a large bundt pan with cooking spray. Add the butter, water, oil, and cocoa to a medium saucepan and bring to a boil.
Meanwhile, whisk together flour, sugar, and salt in a mixing bowl. Pour the chocolate mixture into the bowl with the dry ingredients and mix well. Add the buttermilk and baking soda. Mix together the eggs, cinnamon, and vanilla in a small bowl, and add to the batter. Pour batter into prepared pan.
Bake 45 minutes or until you insert a toothpick in the middle of the cake and it comes out clean. Allow cake to cool completely in the pan.