Measure flour onto a flat surface (ie. kitchen counter); make a well in the center and sprinkle in the sugar. Roughly chop in butter, squeeze on lemon juice, add extract and the egg yolks. (You may add the rind of the lemon, finely grated for added flavor if so desired.) Work all these ingredients into a smooth dough. Form into a ball and chill for several hours.
Remove dough from refrigerator and cut dough into fourths. Working with 1/4 of the dough at a time, roll out to approximately 3/16th of an inch. Cut out circles with a cookie cutter. In half of these cookies cut out a smaller circle in the center with the aid of a thimble (these will be the cookie tops) !
Place on an ungreased cookie sheet and bake at 350 degrees for about 10 minutes but watch them carefully for they suddenly go from browned to burned! Gather up the scraps, adding to another 1/4 piece of the dough and continue cutting out cookies until all the dough is used up. When they have baked and then cooled sufficiently sandwich a solid cookie together with one that has a circle cut in the center using the fruit preserves. Sprinkle tops with confectioners' sugar. Makes about 2 1/2 dozen sandwich cookies.