Preheat the oven to 170°C, and lightly coat 6 muffin cups with nonstick cooking spray.
In a small bowl, whisk together the flour, baking powder, bi carbonate or soda, salt, and lemon zest. In a separate bowl, whisk together the coconut oil, egg white, and vanilla. Stir in the agave and Greek yogurt, mixing until no large lumps remain. Stir in the lemon juice. Alternate between adding the flour mixture and milk to the egg mixture, beginning and ending with the flour, and stirring until just barely incorporated. Gently fold in the blueberries.
Divide the batter into the prepared muffin cups. Bake at 170°C for 20-22 minutes, or until the tops feel lightly firm to the touch. Cool in the pan for 10 minutes before carefully transferring to a wire rack.