Preheat oven to 350 degrees Farehenheit.
Generously grease a Bundt pan with butter (we used a heart-shaped pan, but any shape will do.) Set aside.
In a medium mixing bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
In a standing mixer, fitted with its paddle attachment, add the butter and sugar. Beat on medium speed until the mixture is smooth and light in texture (about 5 minutes). Add the eggs, one at a time, beating well and scraping down the bowl after each addition. Add the sour cream and coffee and mix until combined.
Gradually add the dry ingredients just until incorporated.
Pour the batter into the prepared Bundt pan and bake until the center of cake springs back when touched and a skewer inserted near the center comes out clean (about 45-50 minutes).
Remove the cake from the oven and pour Butter Coffee Pour Over mixture over the hot cake. Let cool completely in the pan on a wire rack. Release the sides and bottom of the cake from the pan with a narrow metal spatula or knife. Invert the pan onto a plate or cake stand. Remove the pan and dust with cocoa powder or powdered sugar before serving.