Line an 8x8-inch baking pan with foil in both directions. Allow a few inches tohang off the ends. Brush foil with melted butter or shortening. Set aside.
Mix together flour, baking powder and salt. In a separate bowl, cream together butter and sugars. Addegg and lemon. Add to dry mixture.
Spread dough evenly over bottom of the pan. Dot with jam.Use a knife to swirl into dough. Bake at 350 for about 30 minutes until an inserted toothpick comes out clean.
Allow pan to cool about 10 to 15 minutes before removing blondies with foil intact. Lift foil by overlap "handles" and set on rack to finish cooling. Cut cooled blondies into desired sizes.