Preheat oven to 375°F. Arrange flat sided baking cups on a sheet pan.
In a medium mixing bowl, sift together flour, baking powder, and salt. Set aside.
In large mixing bowl, beat butter and sugar until light and fluffy; about 4 minutes. Add eggs, one at a time, beating well after each addition. Add lemon extract. Alternately add flour mixture and milk to egg batter. Beat until just combined. Gently fold in blueberries with rubber spatula.
Fill cups 3/4 full. Bake for 20 - 25 minutes or until toothpick inserted in center comes out clean. Remove to wire rack and let cool. May be served warm or at room temperature.