Cream the butter, sugar and salt in a mixing bowl.

Add the flour. Then add the egg yolk.

Using your hands, pull the pastry dough together onto a piece of plastic wrap. Shape the dough into a 6 inch circle. Cover it completely with plastic wrap.

Chill in the fridge for 30 minutes.

Remove from the fridge and roll out between two pieces of plastic wrap into a large circle.

Use the tart shell to "cut" out the dough piece that you will need. Lift that dough into the tart shell and mold it to fit the tart shell. Ensure that you don't have any large tears or holes.

Dock the pastry with a fork and chill for an additional 30 minutes.

Preheat the oven to 350F and prepare the dough for blind baking by adding a piece of aluminum foil and baking beans.

Blind bake for 15 minutes. Remove the baking beans and aluminum foil and bake for an additional 15 minutes. The pastry will be golden brown upon removal. Set aside and cool.

Add the sugar, lemon zest, and lemon juice into your bowl over the double boiler.

Begin adding the butter chunks until melted.

Continue to stir for about 10 minutes.

Check for doneness by seeing if the lemon curd has thickened and if the lemon curd can fully coat the back of a spoon.

Remove from the heat and pass the lemon curd through a sieve.