Preheat oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan.
In a bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.
In another bowl, beat butter and sugar until light and fluffy. Add eggs one at a time, then mix in vanilla.
Gradually add dry ingredients to the wet, alternating with buttermilk. Begin and end with dry ingredients.
Stir in hot coffee (this enhances the chocolate flavor and keeps the cake moist). The batter will be thin — that’s normal!
Pour batter into prepared loaf pan and smooth the top.
Bake for 50–60 minutes or until a toothpick inserted in the center comes out clean.
Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Slice and enjoy!