Tarte au Citron

In a food processor or by hand, combine the flour, icing sugar, and salt. Add the cold cubed butter and pulse until the mixture resembles fine sand — no visible butter chunks. Add the egg yolk and 1–2 teaspoons of cold water and pulse until the dough just comes together. Do not overwork. Press into a flat disc, wrap, and refrigerate for 30 minutes. Roll to 3 mm thickness and line a 22–24 cm fluted tart tin with a removable base. Press gently into the flutes, trim the top neatly, and refrigerate for another 20 minutes. Blind-bake at 180°C (355°F) lined with parchment and weights for 15 minutes, then remove weights and bake a further 10–12 minutes until the base is a uniform pale golden-brown.

In a medium bowl, whisk together the eggs, caster sugar, lemon juice, and lemon zest until the sugar is fully dissolved and the mixture is smooth and uniformly pale yellow. Do not beat to foam — this should be whisked just enough to combine. Set the bowl over a saucepan of barely simmering water (bain-marie), making sure the base of the bowl does not touch the water.

Cook the lemon mixture over the bain-marie, whisking constantly with a flexible spatula or whisk, scraping the sides of the bowl frequently. The mixture will slowly thicken. Continue cooking until it reaches 82°C (180°F) on a thermometer, or the nappe stage: when you draw a finger across the back of a spoon coated in curd, it should leave a clean line. This takes 8–12 minutes. Remove from heat immediately and whisk in the cold butter cubes in two additions, waiting for each to incorporate before adding more. The butter is what makes the curd silky rather than just thick.

Strain the finished warm curd through a fine sieve directly into the cooled tart shell. Gently tap the tin on the counter twice to level the surface and release any air bubbles. Transfer to the refrigerator and chill uncovered for at least 2 hours, or until the curd has set to a sliceable consistency. Serve at room temperature — remove from the fridge 20–30 minutes before serving so the curd softens slightly to its ideal silken texture.