01 - Preheat oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a medium bowl, whisk together the gluten-free flour blend, almond flour, baking powder, and salt until evenly distributed. Set aside.
03 - In a large bowl, beat the softened butter and sugar with an electric mixer on medium speed until light and fluffy, approximately 2 to 3 minutes.
04 - Add the egg, lemon zest, lemon juice, and vanilla extract to the butter mixture. Beat until well combined and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until a soft, cohesive dough forms.
06 - Gently fold the chopped pistachios into the dough using a spatula, distributing them evenly throughout.
07 - Scoop tablespoon-sized portions of dough and roll into balls. Place them on the prepared baking sheets, spacing approximately 2 inches apart.
08 - Gently flatten each dough ball with your fingertips or the bottom of a glass. Sprinkle the top of each cookie with a pinch of granulated sugar for a subtle crunch.
09 - Bake for 13 to 15 minutes, or until the edges are lightly golden and the centers are just set.
10 - Allow the cookies to rest on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving.