In a food processor, combine unsalted butter and superfine sugar. Pulse until smooth and creamy, about 1-2 minutes.

Add 1 whole egg, 1 egg yolk, and vanilla extract, pulsing until fully combined.

Gradually sift in cake flour and salt, mixing until a cohesive dough forms. Wrap in plastic wrap and refrigerate for 1 hour.

Preheat the oven to 140°C (290°F). Brush mini tart tins with melted butter.

Roll out chilled dough to about ½ cm thick on a floured surface. Use a round cutter to cut out discs.

Press the discs gently into the prepared tart tins.

Line tart shells with parchment paper and add baking weights.

Blind bake for approximately 15 minutes or until light golden brown.

In a mixing bowl, whisk together condensed milk, 3 egg yolks, freshly squeezed lemon juice, and lemon zest.

Fill each pre-baked tart shell with the lemon mixture.

Return lemon-filled tarts to the oven at 160°C (320°F). Bake for 10-15 minutes until filling is set.

Allow to cool in the tins for 15 minutes, then transfer to a wire rack.

Set up a double boiler and whisk egg whites and sugar until fully dissolved.

Transfer to a stand mixer and beat on high until stiff peaks form, about 10 minutes.

Pipe the meringue onto each cooled tart, creating peaks and swirls.

Torch meringue until golden-brown for that signature toasted look.