Stir the flour, cream of tartar, soda, salt and sugar together in a large bowl.
Mix the cream with the juice in a jug and pour into the flour mix gradually, stirring it with a spoon (or use a standing mixer with a paddle attachment on low setting).
Turn the shaggy dough out onto a floured surface and knead gently a few times, so that it comes together. Flatten it down to a disc about 2cm thick.
Cut the scones with a 5cm (2 in.) round cutter or similar; press the cutter down without twisting.
Place the scones in a deep baking tray lined with parchment.
Let them stand for 15 minutes while you preheat the oven to 200C/400F/gas 6.
Mix together the extra 1 tbsp. of cream and juice and brush the tops of the scones. Sprinkle them with palm or demerara sugar.
Bake for 15 minutes until coloured on top, cool in the tray for 5 minutes and then take them out onto a wire rack.
