Preheat your oven to 350°F (175°C) and line a muffin tin with parchment paper liners.
In a large mixing bowl, whisk together the Greek yogurt, egg, and vanilla extract until the mixture is completely smooth.
Add the oat flour, vanilla protein powder, baking powder, and sea salt to the wet ingredients, stirring until just combined without overmixing.
Gently fold the fresh blueberries into the batter using a spatula to keep them whole.
In a small separate bowl, combine the almond flour, ground cinnamon, and maple syrup, mixing with a fork until a crumbly streusel texture forms.
Divide the muffin batter evenly among the prepared muffin liners, filling them about three-quarters full.
Sprinkle the almond-cinnamon streusel topping evenly over the top of each muffin.
Bake for 20 to 22 minutes, or until the muffins are golden on top 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 to cool completely.