Butter a 8x4" loaf pan and "flour" with cocoa (let's keep this chocolate cake brown, shall we?!) In a small saucepan whisk together the cocoa and ½ cup water and bring to a boil. Remove from heat and add baking soda and coffee. Set aside to cool.
Preheat oven to 350F.
Whisk together the eggs, sugar, and oil in a large bowl until combined. Whisk in the vanilla. In a separate bowl whisk together the flour, baking powder, and salt. Slowly whisk dry ingredients into wet. Gently stir in the cocoa mixture. Pour into the pan and tap to remove air bubbles. Bake for about 45 minutes or until the cake is risen and a knife inserted comes out clean. Cool for 15 minutes and unmold onto a serving dish. (Cake may be too moist and stick to a cooling rack.) Dust with powdered sugar, if desired, and serve with coffee or tea.