Prepare the Dough:

• Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
• In a medium bowl, whisk together the gluten-free flour, baking powder, and kosher salt. Set aside.
• In a large mixing bowl, use an electric mixer to cream the softened butter and granulated sugar until light and fluffy (about 2–3 minutes).
• Prepare a cornstarch slurry by mixing the cornstarch with water. Add the slurry, milk, lemon juice, and lemon zest to the butter mixture. Beat until fully incorporated.
• Gradually add the dry ingredients to the wet mixture, stirring gently until a dough forms. Do not overmix.
• Fold in the chopped frozen raspberries carefully to avoid over-mixing or crushing the berries.

Shape and Bake:

• Using a cookie scoop or spoon, portion out the dough into balls (about 1½ tablespoons each) and place them on the prepared baking sheet. Leave 2 inches of space between each cookie.
• Combine the granulated sugar and lemon zest to make the lemon sugar. Sprinkle it generously over the tops of the cookie dough balls.
• Bake for 12–14 minutes, or until the edges are lightly golden.
• Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.

Prepare the Glaze:

• In a small bowl, mash the frozen raspberries with water to create a light puree.
• Sift the confectioners’ sugar into the raspberry puree and stir until smooth. Add more water for a thinner glaze, if needed.

Glaze the Cookies:

• Once the cookies have completely cooled, drizzle or spread the glaze over each cookie.
• Let the glaze set for 10–15 minutes before serving.