• In a medium bowl, whisk the flour and salt together and set aside.
• In a bowl of a stand mixer fitted with the paddle attachment or a medium bowl with a hand mixer, cream the butter and sugar on medium speed until smooth and creamy. Scrape down the sides of the bowl and add the egg, extract and the lemon zest and mix until incorporated.
• While the mixer is running low, add the flour and mix until just incorporated. There should not be any traces of white flour.
• Divide the dough into two balls and wrap each ball loosely with plastic wrap. Press the dough to flatten into round disks. Re-wrap tightly, place the dough in the refrigerator and chill for 1-2 hours. This gives the dough time for the flavors to mingle together and become easy to handle.
• When the dough has chilled, preheat the oven to 350 F and line the baking sheet with parchment paper or a silicone mat.
• Remove the dough from the refrigerator. Flour the work surface and the rolling pin for rolling the dough. You can roll the dough in between two parchment sheets to reduce the use of flour. Roll out the dough into 1/8 inch thick, use a fluted cookie cutter to cut into circle shapes. Gather the pieces and re-roll until all is used, chill the dough if necessary. Repeat the same process for the second dough.
• Arrange the cookies onto a baking sheet 1 inch apart, cut the center of the half of the cookie circle where they are on the baking sheet. Place the baking sheet with cookies in the refrigerator for about 10 minutes to firm up before baking.
• Bake the cookies in the preheated oven for 11 minutes or until the edges are light brown in color.
• Let the cookies cool in the baking sheet for about 5 minutes, then use an offset spatula to transfer the cookie onto a wire rack to cool completely. Continue with all the cookies until they are all baked.

Filling

• Use a small offset spatula to spread a ½ teaspoon of jam onto bottom of the whole cookie base and spread the jam on the cookie. Carefully top each with the top cookie and press down gently to make the sandwich.
• Cookies will stay fresh covered at room temperature for 2 days and in the refrigerator for about a week.