Preheat the oven to 190°C/375°F/Gas mark 5
Rinse the blueberries, (defrost first if frozen), and spread on paper towels to dry thoroughly. Cream the butter, sugar, and lemon peel. Add the sour cream. Beat well.
Sift together the flour, baking powder, and salt. Add the flour mixture alternately with milk to the creamed mixture, beating until smooth after each addition. Lightly fold in the blueberries.
Drop by teaspoonfuls on greased cookie sheets. Bake 10 to 12 minutes. Cool on a wire rack.