Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

Whisk together the gluten-free multipurpose flour, baking powder, poppyseeds, and kosher salt in a small mixing bowl.

Mix granulated sugar with lemon zest in a large bowl, rubbing the zest into the sugar until fragrant.

Combine the dry ingredients into the lemon-sugar mixture and fold until just combined.

Cut the cold unsalted butter into small cubes and work it into the dry mixture until it resembles coarse crumbs.

In a separate bowl, whisk together the kefir, egg, and fresh lemon juice, then gently pour this into the dry ingredients.

Turn the dough onto a floured surface and shape it into a rectangle about 7 inches by 5 inches and 1 inch thick.

Fold and pat down the dough a few times, refrigerating briefly if it becomes sticky.

Shape the dough into a circular disk about 6 inches wide and ¾ to 1 inch thick, then chill in the refrigerator for at least 10 minutes.

Cut the chilled dough into 8 equal triangles and arrange them on the prepared baking sheet.

Brush the scones with kefir and sprinkle raw sugar on top.

Bake the scones for 22 to 26 minutes, until golden brown.

Cool on a wire rack and prepare the glaze by mixing powdered sugar with lemon juice, then drizzle over warm scones.