Preheat oven to 425 F. Line 12-cup muffin tin with paper liners. Set aside.
Zest the lemon and set aside. Juice the lemon and set aside for the glaze.
In a large bowl, mix the flour, baking powder, salt, and 1/3 cup sugar. Make a well in the centre.
In a medium bowl, mix the egg, oil, milk, vanilla, and lemon zest.
Pour the wet ingredients into the dry. Mix gently until mostly blended.
Add the blueberries to the batter. Mix until just blended.
Divide the muffin batter into the 12 muffin cups.
Bake for 15-20 minutes or until a toothpick inserted into the centre comes out clean. Let cool slightly before glazing, about 10 minutes.