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, baking powder, baking soda, and fine sea salt until evenly distributed.
03 - In a large bowl, beat the softened butter and granulated sugar with an electric mixer until pale, light, and fluffy, approximately 2 minutes.
04 - Add the egg, lemon zest, fresh lemon juice, and vanilla extract to the butter mixture. Beat until fully combined and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just incorporated. Do not overmix.
06 - Gently fold the coarsely chopped pistachios into the dough using a spatula until evenly distributed.
07 - Scoop tablespoon-sized portions of dough and roll into even balls. If desired, roll each ball in turbinado sugar for added crunch and sparkle.
08 - Place dough balls 2 inches apart on the prepared baking sheets. Gently flatten each ball with your palm or the bottom of a glass to about 1/2-inch thickness.
09 - Bake for 11 to 13 minutes, rotating pans halfway through, until edges are light golden and centers appear set.
10 - Allow cookies to rest on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving or storing.