Transfer the dough to the prepared pan and press into an even layer.
Cut the butter in until the mixture resembles fine crumbs and it holds together in a ball when squeezed in your hand. Cut the butter into pats and add to the flour mixture.Add in the flour and salt and mix or blitz to combine. In a large bowl or the bowl of a food processor, rub or pulse the sugar and orange zest together until the sugar is a pale orange colour.Lightly grease a nine-inch square pan with non-stick cooking spray and/or line it with a parchment paper sling.
