Whisk together the flour, baking powder, salt, and lemon zest. Set aside.

Using an electric mixer on medium speed, beat the butter and sugar until light and fluffy. Mix in the sour cream. Add the eggs, one at a time, mixing well after each addition. Mix in the lemon juice.

Reduce mixer speed to low. Gradually add the flour mixture, mixing just until combined. Very gently stir in the blueberries.

Drop the dough by 2-tablespoon portions onto the prepared pans. Bake 14 to 18 minutes, or until the edges are lightly browned and the centers appear set.

Cool the cookies on the pans for 10 minutes. Then carefully transfer them to a wire rack to cool completely.

Combine the confectioners' sugar and about half of the lemon juice. Add more juice as needed to attain a thick but pourable consistency.

Top each cookie with about a teaspoonful of glaze. Dollop it on and let it spread, or drizzle it over the tops.

Allow the glaze to set for about 10 minutes before serving.