Mix crumbs with sugar and melted butter until well combined. Press firmly into a 10-inch tart pan, covering the base and sides. Bake for 8–10 minutes or until lightly golden. Let cool.

In a bowl, rub together the sugar and lemon zest until fragrant and golden. Whisk in the egg yolks, whole eggs, and lemon juice. Pour mixture into a saucepan and cook over medium heat, stirring constantly until the curd thickens (about 8–10 minutes). Remove from heat and strain through a fine mesh sieve. Let cool for 5 minutes, then add the cubed butter. Use an immersion blender or regular blender to whip until smooth and glossy.

Immediately pour the lemon filling into the cooled crust and spread evenly.

Chill in the fridge for at least 2 hours, or until set.

In a heatproof bowl, combine egg whites and sugar. Set the bowl over a saucepan of simmering water (double boiler style), whisking constantly until the sugar is fully dissolved and the mixture is warm to the touch (about 160°F )

Remove from heat and beat with an electric mixer on high until stiff, glossy peaks form.