Heat the oven to fan 200°C/Gas 6. Lightly grease a baking tray.
Sift the flour, salt and baking powder in a bowl then rub in the butter until the mixture resembles breadcrumbs, then add the sugar and lemon zest. Keep a spoonful of the beaten egg on one side and add a spoonful of the kefir to it to make an egg glaze and mix the remaining egg and kefir together. Add this mixture to the flour and mix gently until you have a firm, but not sticky dough. Don't over mix! The texture should be between a cake mix and a pastry.
Place on a floured board and gently pat until it is 3cm thick. Dip the 7cm cutter in the flour and use it to cut the scones. Place on a baking tray and brush with the egg glaze.
Bake for 15-20 minutes until risen and golden. Transfer to a wire rack to cool.
