Preheat your oven to 350°F (175°C) and grease a loaf pan or line it with parchment paper.
In a large mixing bowl, combine the almond flour, protein powder, baking powder, baking soda, cinnamon, and salt. Mix well to ensure even distribution of dry ingredients.
In another bowl, whisk together the eggs, Greek yogurt, applesauce, and honey (or maple syrup) until smooth. Gradually add the wet ingredients to the dry ingredients, mixing until just combined. If desired, fold in chopped nuts and dark chocolate chips.
Pour the batter into the prepared loaf pan and smooth the top with a spatula. Bake for 45-50 minutes, or until a toothpick inserted into the center comes out clean.
Allow the loaf to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Slice and serve as desired.