Tarte au citron: serve up a slice of sunshine

There is something inherently uplifting about a lemon. Even in literal or figurative dark times, lemons shine bright – little bumpy orbs of joy that cry out from the fruit bowl or the greengrocers to be turned into something mouth-puckering or, once paired with enough sugar, that perfect balance of sweet-sour. Perhaps I am overly sentimental, but lemons always strike me as cheering, and full of promise. Lemon curd was one of the first things I learnt to make when I began cooking, but I’ve held off turning it into a tart for a while, unable to work out how to create the exact pudding I wanted to eat.

For a long time, I have wanted to make this perfect lemon tart, but have been thwarted in my attempts. I have strong opinions on the ideal tarte au citron: I want a tart almost shocking in its lemoniness, so ridiculously zesty that it elicits inadvertent exclamations on eating. I am not here for an insipid lemon tart. But equally, I want a tart from which I can cut clean slices that wibble onto the plate, holding their shape, from the fluted pastry to the perfect, tapering nose. For a while there seemed no way of squaring the circle: to achieve the former, you have to avoid baking the filling. The flavour of the lemon is muted on baking, and muddied by the cream that tends to be folded into it. A baked lemon tart is still a lovely tart, but it’s a different one: mellow and wobbly – like a lemon-scented custard. The sharpness, the bite of the lemon, is lost. But if you simply spoon curd into the pastry shell, it’s impossible to get that beautiful clean slice: the filling will fall and flop on cutting, and it feels more like individual constituents – pastry, curd – than a cohesive pudding.

But, happily, a solution does exist: the shortest of bakes in an oven – a mere six minutes – to set a terribly sharp curd so that it will slice beautifully without losing any of what makes it so delightful. This tarte au citron is exactly what it should be: lip-zipping, eye-popping, zinging and singing with lemon flavour. It is probably gauche to say that you are proud of a recipe of your own making, but I am deeply proud of this one: I want to thrust it onto people in the street, wear a sandwich board proclaiming its brilliance.

This is a very easy curd to make: essentially, all of the ingredients are bunged into a single pan and stirred over a gentle heat until the mixture thickens and feels heavy on the spoon, glossy and shimmering from the butter. Cooking the zest in the syrup preserves a punchy lemon flavour, but removing it before cooking the curd ensures that perfect silken texture. The pastry is a simple one, enriched with a single egg yolk, but unsweetened so as to act as a foil to that sweetsour filling. It’s fully blind-baked, as once the filling is in the tart, it will only receive an extra few minutes in the oven, and there is no place for soggy pastry in a tarte au citron.

Tarte au citron

Makes: 1 9 inch tart (serves 8)

Takes: 30 minutes, plus chilling

Bakes: 30 minutes

For the pastry

200g plain flour

100g butter

1 egg yolk

½ teaspoon fine salt

1 egg white

For the filling

5 small lemons, zest and juice

3 egg yolks

3 whole eggs

100g caster sugar

½ teaspoon salt

100g butter

180°C for 6 minutes to set the tart

1. First make pastry. Rub together the flour, salt and butter until they resemble breadcrumbs. Add the egg yolk and, using a knife, begin to cut the yolk into the crumbed flour and butter. Get your hands stuck in and bring the dough together: if it remains really crumbly, you can add a few drops of cold water to help it along the way. Wrap in clingfilm and refrigerate for at least 30 minutes.
2. Once chilled, remove the pastry from the fridge. Roll the pastry out on a lightly floured worktop into a rough circle the thickness of a pound coin. Lightly dust the pastry with flour and roll the pastry up onto the rolling pin, then lay it gently onto a 9 inch loose-bottomed tart tin. Using a spare ball of dough, ease the pastry into the tin so it sits flush against the curves and any grooves. Prick all over with a fork, cover with oven-safe clingfilm or baking paper, and refrigerate for at least 30 minutes.
3. Preheat the oven to 180°C. Pour dried beans or rice onto the clingfilmed tart tin right up to the brim, then bake for 20 minutes until the pastry is dry to the touch. Remove the dried beans or rice and the clingfilm, and return the tart case to the oven for another five minutes until it is light golden coloured.
4. Remove from the oven and brush the pastry with a little egg white, to seal the pastry: the residual heat will cook the egg white.
5. Next, make the curd: heat the zest, juice and sugar over a low heat until the sugar has dissolved, before sieving out the zest and reserving the lemon syrup. Place this syrup in a bain marie (a heatproof bowl sitting on top of a pan of simmering water) with the egg yolks, whole eggs, salt and butter to the pan, and cook over a gentle heat, stirring constantly, until the mixture thickens and coats the back of a spoon.
6. Push the curd through a sieve and spoon it into the pastry case, jiggling it gently to level out the filling. Bake in the oven (still at 180°C) just for 6 minutes to set the filling. Allow to cool before transferring to the fridge and chilling entirely. Remove from the tin carefully and slice to serve.