Preheat the oven to 180°C (356°F).
Add soy milk, erythritol, cocoa powder, baking powder, almond flour, and protein powder to a bowl and mix evenly.
Melt coconut oil and add it to the batter, then mix again.
Pour the batter into a pound cake mold.
Bake at 180°C (356°F) for 25 minutes.
Remove, let cool, and slice for serving.