Rub the lemon zest into the sugar. Mix in flour, baking powder, xanthan and salt. Rub in the cold butter, leaving a few pea-size pieces.

Stir in the cold yogurt and vanilla. The mixture will still look dry. Add the chopped strawberries and mix gently until most flour is hydrated; the dough should remain shaggy.

Tip onto a lightly floured surface and press together without a long knead. Add only a little extra yogurt if it cannot hold together, or a little flour if excessively sticky. Press to a 7-inch disc about 1 inch thick and cut into eight wedges. Cover on a lined tray and refrigerate at least 20 minutes.

Heat a conventional oven to 400°F / 200°C. Place the chilled wedges on a fresh lined baking tray with generous gaps. Mix the brushing yogurt and milk and brush over the tops.

Bake 20–22 minutes, until golden with deeper-colored edges. Rest 5–10 minutes on the tray, then transfer to a rack and cool until barely warm or at room temperature.

Mash the glaze strawberries and whisk with powdered sugar and vanilla. Keep the glaze fairly thick; adjust with tiny amounts of berry mash or sugar only if needed. Spoon over cooled scones and allow 10–15 minutes to set.