In the bowl of a stand mixture. Cream together the butter and sugar until light and fluffy.
Add the egg and vanilla and mix in thoroughly, followed by the citrus zest.
Stir in the salt and baking powder. Add in the flour, and run the mixer until the dough just comes together.
Gather the dough and shake it into a flattened disk. Wrap in saran wrap and chill dough for 2 hours.
Flour a work surface and roll dough out to 1/8" thickness. Using cookie cutters, cut dough into circles. Cut a smaller circle out of half of the cutouts. Place on a cookie sheet sprayed with nonstick spray, and chill in the refrigerator for 15 minutes.
Preheat the oven to 350.
Place chilled cookie sheets in the oven for 12-15 minutes, or until the cookies have started to turn golden. Let cool on the cookie sheet for a few minutes, then remove to a cooling rack using a small spatula. Cool completely
Spread each "solid" cutout with jam, then top with a "hollow" cut out. Dust with powdered sugar.