Preheat oven to 350 F. Butter and flour bottom and sides of a 10-inch tube pan. Set aside. In large bowl of mixer, cream together butter and sugar at high speed until light and fluffy. Add eggs, one at a time, beating well after each addition. Set aside. In a separate bowl, sift together flour, baking powder and salt. In a medium bowl, mix the milk, lemon extract, lemon juice and zest. Add the dry and wet ingredients alternately to butter mixture, beginning and ending with dry. Sprinkle blueberries with 2 tablespoons flour and gently toss. Remove from flour and lightly fold into batter just to distribute well. Spread batter into prepared pan. Bake 80-90 minutes or until a sharp knife insert into center comes out clean. Allow to cool 10 minutes in pan then invert onto a cooling rack. Cool completely before slicing. Frost if desired or sprinkle with powdered sugar.