In a medium bowl, mix flour, baking powder and salt. Beat butter, sugar, egg, lemon juice and zest in large bowl. Beat in flour mixture. Divide into 2 halves and flatten. Wrap in plastic; chill 1 hour.
Heat oven to 350°F. Line baking sheets with nonstick foil. Roll half of dough 1/8 inch thick on floured surface. Cut out 24 cookies with 2-1/4-inch round cutter. Repeat with remaining dough for 48 cookies total. Transfer to baking sheets. Cut a 1-inch hole in center of 24 of the cookies. Remove centers and reroll for a total of 30 rounds and 30 cutouts. Bake at 350°F for 13 minutes, until brown around edges. Cool on rack.
Spread 1/2 teaspoon jam on each cookie round. Dust cut-outs with confectioners' sugar. Place on jam-covered cookies.