1. Put the flour, salt, bicarbonate of soda and cream of tartar into a mixing bowl.
2. Stir the sugar and the sultanas into the flour, and make a slight well in the centre.
3. In a jug, mix together the yoghurt and the milk. Pour this mixture gradually into the well in the flour, and mix with a round-bladed knife, to form a firm but not too stiff dough.
4. Turn the dough onto a floured board and knead it until it is smooth.
5. Form the dough into a round, and slightly flatten it with your hand.
6. Cut a deep cross into the top of the dough and brush with a little extra milk. Put the loaf onto a lightly floured baking sheet, and bake in the centre of a preheated oven, 200°C/400°F/Gas Mark 6, for 25 minutes.
7. Turn the loaf upside down on the tray and return it to the oven for a further 5 minutes to cook underneath.
8. Wrap the loaf in a damp cloth and place it on its side to cool.