Preheat oven to 350°F (175°C). Line a muffin tin with paper liners or lightly grease it.
In a large bowl, whisk all dry ingredients: almond flour, protein powder, baking powder, baking soda, cinnamon, and salt.
In a separate bowl, whisk together wet ingredients: eggs, maple syrup, almond milk, coconut oil, vanilla, and mashed banana (if using).
Pour the wet ingredients into the dry and stir until just combined. Don’t overmix.
Gently fold in add-ins like blueberries or nuts.
Spoon batter evenly into muffin cups, filling each about ¾ full.
Bake for 18–22 minutes, or until a toothpick inserted in the center comes out clean.
Cool muffins in the pan for 5 minutes, then transfer to a wire rack to cool completely.