Zest and juice the lemons. Set aside zest (for the dough and sugar coating) and juice.

Roughly chop frozen raspberries and return them to the freezer.

In a bowl, whisk together the gluten‑free flour, baking powder, and salt.

In a mixer, beat the butter and 1¼ cups sugar until creamy (2–3 minutes).

Add the cornstarch slurry, milk, lemon zest (1 Tbsp), and lemon juice, mixing until pale yellow and chunky.

Gradually add the dry ingredients until just combined. Fold in frozen raspberries—dough should appear marbled pink.

Cover and freeze the dough for at least 1 hour (mandatory to prevent spreading).

Preheat oven to 325 °F (163 °C). Line a baking sheet with parchment.

Mix together 3 Tbsp sugar and 1 tsp lemon zest to make the lemon sugar coating.

Scoop dough (ice cream or large cookie scoop—makes ~11 large cookies), roll in lemon sugar to coat.

Place dough balls 3–4 in apart on the tray. Bake for 15–16 minutes. Immediately use a spatula to reshape into rounds; cool on the sheet for 5 minutes, then transfer to a wire rack.

If using glaze: Mix confectioners’ sugar, raspberries, and water until smooth. Drizzle over completely cooled cookies, let glaze set, and finish with extra lemon zest if desired.