Pastry:

In a bowl, mix softened butter and powdered sugar.

Beat in the egg. Add flour and mix just until a uniform dough forms.

Press the dough with your hands onto the bottom and sides of a lined baking dish.

Prick with a fork, refrigerate for about half an hour, then bake at 180 degrees for 12-15 minutes, until golden.

 

Lemon cream:

In a saucepan, combine eggs, sugar, lemon juice, and lemon zest, and whisk well.

Cook the mixture over medium heat, stirring constantly, until it thickens into a uniform and thick cream.

Remove from heat, add butter, and stir until melted into the cream. The cream will be thin at this stage, and that's okay.

Transfer the cream to a sealed container and chill in the refrigerator for 2-3 hours or until completely cold.

Fill the baked pastry with the chilled cream up to the top and smooth it out.

 

Meringue:

Place a heatproof bowl over a saucepan of simmering water to prepare the meringue using the double boiler method.

In the bowl, combine egg whites and sugar, stirring constantly until the sugar dissolves (you can check with your fingers that there are no grains).

Once the sugar has dissolved, whip the egg white and sugar mixture for about ten minutes, until the sides of the bowl cool and there's a stable and stiff foam.

Drizzle over the meringue or spread with a spatula. 

Bake the pie in an oven preheated to 250 degrees for 3-5 minutes until the top layer turns golden brown or using a torch.