01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together the gluten-free flour, baking soda, and salt. Set aside.
03 - In a large mixing bowl, cream the softened butter and sugar together until light and fluffy, about 2–3 minutes.
04 - Beat in the egg, then add the lemon zest, lemon juice, and vanilla extract, mixing until well combined.
05 - Gradually add the dry ingredients to the wet mixture, mixing until just combined.
06 - Fold in the chopped pistachios until evenly distributed throughout the dough.
07 - Using a tablespoon or small cookie scoop, drop dough onto prepared baking sheets, spacing about 2 inches apart. Sprinkle each cookie with finely chopped pistachios if desired.
08 - Bake for 10–12 minutes, or until the edges are lightly golden.
09 - Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.