Preheat the oven to 350°F (175°C) and prepare your baking pan.
In a large mixing bowl, combine the almond flour, cocoa powder, protein powder, erythritol, and baking powder.
In another bowl, whisk the eggs, almond milk, applesauce, and vanilla extract together until well combined.
Pour the wet mixture into the dry ingredients and mix until just combined.
Pour the batter into the prepared baking pan and smooth the top with a spatula.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Once baked, allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
Once cooled, slice and serve the cake as desired.