Preheat your oven to 175°C (350°F). Grease a 9x5 inch loaf pan thoroughly with butter and dust with cocoa powder to prevent sticking.
In a large bowl, sift together the flour, cocoa powder, and baking powder. Set aside to ensure an even, lump-free dry mixture.
Using a mixer, beat the softened butter and sugar on medium speed until the mixture is pale, fluffy, and aromatic—about 3-4 minutes. You should see it turn a lighter shade and feel soft to the touch.
One at a time, add the eggs to the creamed mixture, beating well after each addition. Then, mix in the vanilla extract until the batter is smooth and cohesive.
Gradually add the dry ingredients to the wet mixture in three parts, alternating with a splash of hot water or espresso. Mix gently on low speed just until everything is combined—be careful not to overmix to keep the crumb tender.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula. Tap the pan gently on the counter to release any air bubbles and even out the surface.
Bake in the oven for 55 to 60 minutes. The cake is ready when the top is glossy and crackled, and a toothpick inserted into the center comes out with moist crumbs. The edges might pull slightly away from the pan.
Remove the cake from the oven and let it cool in the pan for about 15 minutes. Then, transfer it to a wire rack and cool completely before slicing to allow the crumb to set properly.
Once cooled, slice the cake with a sharp knife and serve. For an extra touch, dust lightly with cocoa powder or drizzle with melted chocolate if desired.
