In a large mixing bowl, cream butter and sugar until light and fluffy. Beat in egg and vanilla, Combine the flour baking powder and salt, gradually add to the creamed mixture and mix well.
Divided the dough into 4 equal portions, shape each into 12-inch x 3/4 inch roll. Place 4 " apart on two gresed baking sheets. ( 2 on each sheet ) Make 1/2 inch depression down the center of each log , fill with jam, Bake at 350 for 15-20 minutes or until lightly browned. Cool for 2 minutes , Cut diagonally into 3/4 inch slices. remove to wire rack to cool.