In large bowl of an electric mixer, beat butter until creamy; gradually add granulated sugar, beating until smoothly blended.
Beat in lemon peel and egg.
In another bowl, stir together flour, baking powder, and salt; add to butter mixture alternately with milk, blending thoroughly.
Gently stir in blueberries.
Drop dough by rounded tablespoonfuls onto greased baking sheets, spacing cookies about 2 inches apart.
Bake in a 375Â° oven for about 15 minutes or until golden brown.
Transfer to racks and let cool for 5 minutes; then sift powdered sugar lightly over tops.