
Heat the oven to 375ºF.
Cream butter with lemon zest and 1 cup of the sugar until light and fluffy.
Add the egg and vanilla and beat until combined.
Toss the blueberries with ¼ cup of flour.
Whisk together the remaining flour, baking powder, and salt.
Add the flour mixture to the batter a little at a time, alternating with the milk. Fold in the blueberries.
Grease a muffin tin. Distribute batter among muffin cups and sprinkle with remaining sugar.
Bake for 30 minutes, checking for doneness.
Let muffins cool in the pan for about 7 minutes before serving.