Whisk together the flour, cinnamon, and salt (if using) in a medium bowl. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium-high speed until smooth, fluffy and creamy, about 2 minutes.
Add the egg yolk and vanilla extract, and beat until combined, about 1 minute. Scrape down the sides and bottom of the bowl and beat again as needed to ensure everything is combined.
Add the flour mixture and the ground pistachios and mix on low until combined. It will be crumbly at first, but will come together after a couple minutes of mixing. Stop mixing when large clumps have formed and there are no big pockets of flour.
Turn out the dough onto a sheet of plastic wrap. Flatten into a disc, and wrap in plastic wrap. Chill the dough in the refrigerator for 1 hour.
Line two baking sheets with parchment paper, and set aside.
Generously flour a work surface, as well as your hands and the rolling pin. The dough may become sticky as you work, so keep extra flour nearby to use as needed. You can roll out the dough between two pieces of wax paper or parchment paper to prevent any sticking issues if you wish.
Roll out the disc until ¼ inch thick. Using a 2½ inch scalloped cutter, cut the dough into circles. Re-roll the remaining dough and continue cutting until all is used. You should have 24 cookies.
Place the cookies 2" apart on the baking sheets.
Using a 1" round or scalloped cutter, cut a hole into the center of 12 of the cookies.
Place the cookies into the refrigerator to chill for an additional 20-30 minutes. Meanwhile, preheat the oven to 350F.
Bake the cookies for 14-16 minutes, or until the edges are just beginning to turn brown. Let them cool for 5 minutes on the pan, then transfer to a rack to cool completely.
Place the cookies with the holes in them on a cookie sheet and sift confectioners' sugar over the top.
Spread ¾ teaspoon of jam on each whole cookie. Carefully top each with a sugar dusted hole cookie and press down gently to create a cookie sandwich.
Cookies will stay fresh covered at room temperature for 2-3 days or in the refrigerator for up to 1 week. They can also be frozen unfilled for up to 2 months.