Measure out the flour, salt and baking powder into another, large mixing bowl and add the butter. Rub the butter into the flour, then add the yoghurt mixture. Bring together using your hands, or a wooden spoon, to form a rough dough. Try not to overwork it. Gently incorporate the raspberries (I try to keep their shape as much as possible). The mixture will get rather sticky at this point. Lightly dust your work surface and place the dough on top.