Preheat your oven to 180°C (350°F). Grease a 9x5 inch loaf pan with butter and dust lightly with cocoa powder to prevent sticking.
In a small bowl, whisk together the cocoa powder and hot water until smooth and glossy. Set aside to cool slightly; this will intensify the chocolate flavor.
In a large mixing bowl, cream the softened butter and sugar together using a whisk or electric mixer until the mixture is light, fluffy, and pale in color—about 3 to 4 minutes. You should hear a soft, rhythmic sound as the mixture whips.
Add the eggs one at a time, beating well after each addition, and scraping down the sides of the bowl to ensure everything is evenly incorporated. The batter should become smooth and slightly thickened.
Pour the cooled cocoa mixture into the batter and add the vanilla extract. Mix just until combined, creating a rich, chocolatey base.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet batter, mixing on low speed or folding gently with a spatula until just combined. Do not overmix—lumps are okay and help keep the cake tender.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula. Gently tap the pan on the counter to release any air bubbles trapped inside.
Bake in the preheated oven for 55 to 60 minutes. Check for doneness by inserting a toothpick into the center; it should come out with moist crumbs but no wet batter. The top will be crackled and slightly firm to the touch.
Remove the cake from the oven and let it cool in the pan for 15 minutes. Then, transfer it to a wire rack to cool completely—about 30 minutes. This cooling period helps set the crumb and prevents crumbling.
Once cooled, dust the top lightly with cocoa powder or smoked sea salt for an added flavor boost. Slice with a serrated knife and serve to enjoy the velvety, chocolatey richness with a subtle smoky twist.
