01 - Preheat oven to 350°F (175°C). 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.
03 - In a large bowl, beat the softened butter and granulated sugar together using an electric mixer or whisk until light and fluffy, approximately 2 minutes.
04 - Add the egg, vanilla extract, lemon zest, and fresh lemon juice to the butter mixture. Beat until well combined and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing just until incorporated. Do not overmix.
06 - Gently fold the coarsely chopped pistachios into the dough until evenly distributed.
07 - Scoop dough by rounded tablespoons onto the prepared baking sheets, spacing each portion 2 inches apart. Flatten each scoop gently with the back of a spoon.
08 - Bake for 12 to 14 minutes, or until the edges are golden and the centers are set.
09 - Allow the cookies to cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving or storing.