01 - Preheat oven to 350°F. Line two baking trays with parchment paper and set aside.
02 - In a large mixing bowl, whisk together the all-purpose flour, powdered sugar, cornstarch, and salt until evenly distributed.
03 - Add softened vegan butter, melted coconut oil, vanilla extract, and lemon zest to the dry mixture. Stir and mix until a soft, cohesive dough comes together.
04 - Scoop tablespoon-sized portions of dough and roll into even balls. Place on the prepared baking trays, spacing them about 2 inches apart.
05 - Gently press down each dough ball with your fingers or the tines of a fork to create a uniform flat shape for even baking.
06 - Bake for 10 to 12 minutes, or until the edges are lightly golden. Transfer to a wire cooling rack and let cool completely.
07 - In a bowl, beat powdered sugar and softened vegan butter together until light and fluffy. Mix in the lemon juice, lemon zest, and turmeric if using, and beat until smooth and creamy.
08 - Pipe or spread a small dollop of filling onto the flat side of half the cooled cookies. Press the remaining cookies on top, flat side down, to form sandwich pairs.
09 - Refrigerate the assembled cookies for at least 30 minutes to allow the filling to set and achieve the best texture before serving.