Preheat your oven to 350°F (175°C) and line a muffin tin with silicone liners or lightly grease with coconut oil.
In a large mixing bowl, whisk together the vanilla protein powder, oat flour, baking powder, and sea salt until no clumps remain.
In a separate bowl, combine the Greek yogurt, egg, melted coconut oil, vanilla extract, and lemon juice, whisking until the mixture is completely smooth.
Gradually add the dry ingredients into the wet ingredients, stirring with a spatula until just combined; avoid over-mixing to keep the texture light.
Gently fold in the fresh blueberries and the lemon zest so they are evenly distributed throughout the batter.
Divide the batter evenly among the prepared muffin cups, filling each about three-quarters full.
Bake for 18 to 22 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.
While the muffins cool, whisk together the monk fruit sweetener and a small amount of extra lemon juice in a small bowl to create a thin glaze.
Drizzle the lemon glaze over the muffins once they have reached room temperature and enjoy.