Position a rack on the lower third of the oven and preheat to 350°F. Grease a 9x5x3 inch loaf pan, dust it with flour and tap out the excess. Line the bottom with parchment paper.

Sift the flour, cocoa, baking powder and salt together twice then set aside. Using a hand mixer on low speed, beat the butter for 1 minute or until light. Add the sugar, about 2 tablespoons at a time, beating as you go. Once all the sugar is added, continue beating on medium speed for another 2-3 minutes, until the mixture is fluffy.

Add the eggs one at a time, beating for about 10 seconds between additions. Scrape down the sides of the bowl and beat for another minute then add the vanilla.

Fold the sifted ingredients into the batter in three additions, alternating with the water (or milk) in two additions. Once everything is combined beat the batter on low speed for another minute until it's smooth.

Transfer the batter to the prepared loaf pan, smooth the top and tap the pan on the counter to break up any air bubbles in the batter. Bake for about 1 hour and 10 minutes or until a tester inserted in the center comes out dry.

Cool the cake in the pan on a wire rack for 30 minutes before serving.