Preheat the oven to 325°F (165°C). Lightly grease a standard loaf tin and line it with parchment paper, leaving an overhang on the sides. Set aside.
Sift the cake flour and cocoa powder into a medium-sized bowl. Add the salt and whisk well to combine. Set aside.
1 ¼ cups cake & pastry flour, ½ cup cocoa powder, ½ teaspoon salt
Add the softened butter to the bowl of a stand mixer. Using the paddle attachment, beat the butter on medium-low speed for one minute. With the mixer running, add the sugar a bit at a time. Once all of the sugar is added, stop the mixer and scrape down the sides of the bowl. Increase the speed of the mixer to medium and continue to cream the butter and sugar together for 5 minutes, stopping to scrape down the sides of the bowl halfway. The mixture should be much lighter in color and fluffy in texture.
1 cup butter, 1 ¼ cups granulated sugar
Add the eggs one at a time, mixing well between each addition.
4 large eggs
Next, add the dry ingredients to the wet mixture. Mix on low until the flour is almost mixed in. Switch to a wooden spoon or spatula. Gently finish folding the batter by hand until the flour is just combined. Be careful not to overmix to ensure a tender crumb.
Spoon the batter into the prepared pan. It will be quite thick and creamy, almost like chocolate mousse. Place the tin in the oven and bake for 55-60 minutes, or until a toothpick inserted into the center comes out with only a few crumbs.
Let the cake cool in the pan for 10 to 15 minutes. Use the parchment paper overhang to lift the cake from the pan to the rack to cool completely.
Notes
This recipe has an equal flour, butter, sugar, and egg ratio, making the cake heavier and dense like a traditional old-fashioned pound cake. If you like a lighter, fluffier cake with more moisture, add ½ cup (125 ml) of buttermilk or ½ cup (113 g) sour cream to the wet ingredients after adding the eggs. If using buttermilk or sour cream, add ¼ teaspoon of baking soda to neutralize the acidity and help the cake rise properly.