Preheat your oven to 350°F (175°C) and line a muffin tin with silicone or paper liners.
In a large mixing bowl, whisk together the oat flour, vanilla protein powder, baking powder, and sea salt.
Add the Greek yogurt, egg white, and almond milk to the dry ingredients, stirring until a thick, smooth batter forms.
Gently fold the fresh blueberries into the batter using a spatula to avoid crushing them.
In a separate small bowl, combine the almond flour, coconut oil, and ground cinnamon, mixing with a fork until the texture is crumbly.
Distribute the muffin batter evenly among the prepared muffin cups.
Sprinkle the almond-cinnamon streusel topping over the center of each muffin.
Bake for 18 to 22 minutes, or until the tops are firm to the touch and a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the tin for 5 minutes before transferring them to a wire rack.