Preheat oven to 350 degrees. Combine flour, baking powder and salt. Set aside.
In a mixing bowl, using a mixer, beat butter with sugar until fluffy. Beat in egg and vanilla, then gradually add flour mixture. Mix until a dough ball forms. Divide dough in half.
On a floured surface, roll out dough to about 1/4 inch thickness. Using a 2 1/2 inch round cookie cutter, use first half to cut solid cookies. Then roll out second half for the tops (which have a small cutout in the center) and bake in preheated oven for about 9 minutes. Remove from oven and place on wire racks to cool.
When cool, spread solid bottom cookies with jam and place cutout top cookie on top. Sprinkle with powdered sugar. It is best to use a Linzer cookie cutter which is available at cake and candy stores everywhere, but you can also use a 2 1/2 inch round cookie cutter and for the center cut out use a 1 inch cookie cutter. Makes about 3 dozen. Enjoy!