Preheat your oven to 350°F (175°C). Line a large baking sheet with parchment paper or a silicone baking mat to prevent the cookies from sticking.
In a medium-sized bowl, whisk together the oat flour, vanilla protein powder, baking powder, and salt. Stir in the fresh lemon zest, ensuring it is evenly distributed throughout the flour mixture.
In a separate large bowl, whisk the egg until smooth. Add the Greek yogurt, maple syrup, and lemon juice. Mix well until the liquid ingredients are fully incorporated and creamy.
Gradually pour the dry ingredients into the wet ingredients. Use a spatula to fold the mixture together until a thick dough forms. Be careful not to overmix, as this can make the cookies tough.
Gently fold the fresh blueberries into the dough. Do this carefully so the berries don’t burst and turn the entire dough blue.
Using a cookie scoop or a tablespoon, drop rounded portions of dough onto the prepared baking sheet. Flatten them slightly with the back of a spoon. Bake for 10-12 minutes, or until the edges are lightly golden. Allow them to cool on the pan for 5 minutes before transferring to a wire rack.