1. Preheat over to 425F. Combine flour and sugar in food processor. Distribute butter over flour. With on/off motion cut in butter until mixture resembles coarse bread crumbs. Beat together egg yolk and lemon juice in a small bowl. With machine running, pour mixture through feeder tube. As soon as liquid is incorporated, turn off machine. Turn mixture into bowl and knead together gently until it forms a ball.
2. On a floured board, roll out pastry with a floured rolling pin, until it will fit in a 9-inch tart pan. Cut away excess pastry. If the pastry breaks, patch it with the trimmings. Prick pastry base, line with parchment paper and fill with dried beans or pie weights. Bake for 15 minutes, remove parchment and weights, bake for another 5 minutes. Remove from oven.
3. Reduce heat to 350F. To make filling, whisk together eggs and sugar in a small bowl. Stir in melted butter, lemon rind and lemon juice. Pour into pastry shell.
4. Bake for 15 - 18 minutes or until just set.
5. Sift with icing sugar. Set ove rto broil. To protect pastry, place tinfoil around edge of tart. (Rory's note: you can also use a kitchen torch to do this, and it ensures your crust is not burnt.)Place tart under broiler watching carefully until the sugar turns golden brown. Cool on rack.