Sift flour and salt in a bowl. Cut the chilled butter into cubes and rub into the flour with your fingertips until the mixture looks like breadcrumbs.
Make a well in the center and add the water. Using a butter knife in a cutting motion mix until the mixture comes together. If it looks a little dry you can add a little extra water.
Turn the mixture out onto a floured surface, and pull it together with your hands. Knead it gently for 1-2mins or until it becomes smooth. Shape it into a round and using a knife dipped in flour, lightly mark 8 wedges on the top.
Place it on a baking tray lined with baking paper. Sprinkle the top with flour, and bake for 35mins at 200°C, or until golden and when tapped underneath sounds hollow.
Leave it to cool on a wire rack for 30mins. If you cut it too soon it will look undercooked, however it just needs time to rest before cutting.