In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in extract. Combine flour and baking powder; gradually add to the creamed mixture and mix well.
Press into a greased 13-in. x 9-in. baking pan. With a moistened finger, make diagonal indentations every 2 in. in both directions, about 1/3 in. deep.
Fill indentations with jam. Bake at 350° for 40 minutes or until lightly browned. Cool on a wire rack. Cut into bars.