Preheat the oven to 350°F, and lightly coat 9 standard-sized muffin cups with nonstick cooking spray.Whisk together the coconut flour, protein powder, xanthan gum, baking powder, baking soda, salt, poppy seeds seeds, and lemon zest in a medium bowl. In a separate bowl, whisk together the coconut oil, egg, and vanilla. Stir in the Greek yogurt until no large lumps remain. Stir in the agave, lemon juice, and almond milk. Add in the coconut flour mixture, stirring until fully incorporated. Let the batter rest for 10 minutes. Gently fold in the blueberries.Divide the batter between the prepared muffin cups. Bake at 350°F for 23-26 minutes, or until a toothpick inserted into the center comes out clean. Cool in the pan for 10 minutes before carefully turning out onto a wire rack.