In large bowl, whisk together flour, almonds, icing sugar, lemon rind and salt. Using pastry blender or 2 knives, cut in butter until mixture resembles fine crumbs with a few larger pieces. Stirring briskly with fork, stir in egg yolk until pastry begins to hold together. With hands, knead gently just until pastry holds together. Wrap in plastic wrap. (Make- ahead: Refrigerate for up to 2 days.)
