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.
Meanwhile, toss the blueberries with ¼ cup of flour; then 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. Note: Batter will be thick. This is OK.
Grease a jumbo muffin tin (or a 12-cup muffin tin) with butter or coat with non-stick spray.
Distribute batter among muffin cups.
Sprinkle batter with remaining tablespoon of sugar.
Bake for 30 minutes (or less, roughly 18-25 minutes, if using a 12-cup muffin tin).
Check with a toothpick for doneness. If necessary, return pan to oven for a couple of more minutes.
Let muffins cool in pan for about 7 minutes before serving.
