Preheat oven to 310°F. Butter and flour a 10-inch Bundt cake pan. Set aside.1

In a large bowl whisk flour, sugar, cocoa, baking soda, and salt. Set aside.2

In another large bowl, whisk eggs, buttermilk, and vanilla. Add oil and whisk until smooth.3

Add dry ingredients to egg mixture. Add rum and hot coffee. Mix until combined. Batter will be thin.4

Pour into prepared cake pan. Bake for 60 to 70 minutes, or until a toothpick comes out with a few crumbs. Let cool in pan for 30 minutes, then turn out and cool on a wire rack.5

While cake is cooling, begin to make the chocolate rum syrup. Heat butter, water, sugar, salt, and cocoa in a medium saucepan over medium heat. Bring to a boil, then reduce to low. Simmer for 3 minutes. Remove from heat and stir in vanilla and rum.6

Wash and dry Bundt pan. Place over cooled cake and invert the cake back into pan. Pour syrup over surface of cake. Let soak for 8 hours, or overnight.7

To serve, turn cake out onto a cake plate and dust with confectioners sugar.