Toss blueberries with 1 tablespoon flour; set aside. In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each. Combine remaining flour with baking powder and salt; add alternately with milk to creamed mixture. Fold in lemon zest and berries.
Pour into a greased and floured 9x5-in. loaf pan. Bake at 350° for 60-65 minutes.
Meanwhile, combine glaze ingredients in a small saucepan. Heat to boiling, stirring until sugar dissolves. Cool cake in pan 10 minutes before removing to wire rack. Brush glaze on top and sides of cake. Cool. To serve, cut into 1/2-in. slices.