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 and to ensure even browning.
In a medium-sized mixing bowl, whisk together the oat flour, vanilla protein powder, baking powder, and salt. Ensure there are no large lumps of protein powder for a smooth dough consistency.
In a separate smaller bowl, beat the egg and then stir in the Greek yogurt, maple syrup, lemon zest, and fresh lemon juice. Mix until the liquid ingredients are fully incorporated and smooth.
Pour the wet ingredients into the bowl with the dry ingredients. Use a spatula to stir them together until a thick, slightly sticky dough forms. Avoid overmixing, as this can make the cookies tough.
Gently fold the fresh blueberries into the dough using a spatula. Be careful not to press too hard so the berries remain whole and don’t bleed too much purple juice into the batter.
Scoop the dough into 8 equal portions and place them on the prepared baking sheet. Use the back of a spoon to slightly flatten each mound into a cookie shape. Bake for 10 to 12 minutes, or until the edges are firm and slightly golden.
Remove the tray from the oven and let the cookies rest on the hot pan for 5 minutes. This helps them finish setting. Transfer them to a wire rack to cool completely before eating.