Preheat the oven to gas 6, 200°C, fan 180°C. Mix the flour, baking powder, lemon zest and a pinch of salt in a bowl. Rub in the butter with your fingertips. Stir in the sugar, egg and enough milk to make a soft dough. Handle as little as possible to keep it airy.
Tip onto a floured surface and pat the dough out to a 2cm (1in) thickness. Stamp out as many scones as you can with a 2.5-3cm (1-1½in) cutter, then re-roll and stamp again (you should get about 20). Put the scones in the oven for 12-15 minutes, until risen and golden. Split while still warm, then cool on wire rack.
Fill the scones with lemon curd and cream. Press the tops down gently so they stick.