In a bowl, combine all of the ingredients. Knead into a dough ( it will be very sticky). Cover and refrigerate the dough for 1 hour.
Preheat the oven to 350⁰ F. Line a baking sheet with parchment paper.
Place about 2 tablespoons of confectioners' sugar on a plate. Form the dough into 2 rolls, about 1-inch in diameter and 10-inches long. Cut into pieces about 1-1/2inches long or 9 pieces per roll. Roll each piece between the palms of your hands to smooth each cookie into a log and round the edges. Roll each piece in the confectioners' sugar to coat. Place on the prepared baking sheets. Press down on each cookie to flatten slightly. Bake for 10 minutes. Remove the cookies from the oven and allow to cool.
Pistachio cookies are classic Italian cookies that are soft and tender, loaded with pistachio flavor and gluten free. With just a few simple ingredients these cookies are ready to enjoy after baking for only 10 minutes. I highly recommend the Fiori di Sicilia flavoring but you can substitute an orange extract if desired.