Method

• 1.
  For the pastry, place the flour, sugar, zest and a pinch of fine salt in a food processor and pulse to combine. Add the cold butter and pulse until it resembles fine crumbs. Lightly beat 1 whole egg and 1 egg yolk in a small bowl. Pour mixture into food processor and pulse until incorporated. Turn the mixture onto a clean work surface and knead with your hands until the dough comes together. Wrap dough ball in plastic wrap and press down to form a disc. Chill for at least 30 minutes.
• 2.
  Roll chilled pastry on a lightly floured surface to a 33cm circle, 5mm thick, and use it to line a 24cm x 3cm-high, loose-based tart pan, letting excess pastry overhang. Chill for a further 30 minutes.
• 3.
  Preheat oven to 180°C/160°C fan-forced. Place a baking tray in the oven to heat. Line tart case with baking paper and fill with pastry weights. Bake for 30 minutes on the hot tray. Turn oven down to 160°C/140°C fan-forced. Remove weights and paper and bake for a further 40 minutes, or until deeply and evenly golden. Set aside to cool to room temperature. Using a serrated knife, cut away and discard excess pastry.
• 4.
  To make the curd, combine zest and juice in a large, heatproof bowl placed over a saucepan of simmering water (don’t let base of bowl touch the water). Place cornflour and 21/2 tbs water in a small bowl and stir to combine, then add to lemon mixture and whisk to combine. Add 1 1/4 cups (310ml) boiling water and whisk vigorously for 10 minutes to remove any lumps, or until a jam consistency. Remove from heat, and whisk in yolks, sugar, butter and citric acid until thoroughly combined and smooth. Pour into pastry case, level surface with a spatula and chill until cold.
• 5.
  For meringue, place sugar and 1/4 cup (60ml) water in a medium saucepan along with the rosemary sprigs and stir over low heat until sugar dissolves. Increase heat to high and cook until syrup reaches 115°C on a sugar thermometer, then remove from heat and carefully remove rosemary and discard.
• 6.
  Meanwhile, in a stand mixer fitted with the whisk attachment, whisk egg whites until soft peaks. With the motor running on medium speed, slowly add the hot syrup, then whisk on high for 5 minutes, or until a thick and glossy meringue.
• 7.
  Pile the meringue high on top of chilled tart, using a spatula to swirl the meringue in a decorative pattern. Using a kitchen blowtorch, brown top of meringue until it turns a dark brown colour - the stage just before turning black. Doing this will add a bit of bitterness, offsetting some of the sweetness of the tart. Slice tart to serve.