French Lemon Tart (Tarte au Citron)

Before you start

A tarte au citron is about contrast: a thin, sandy, buttery shell against a filling that is properly sour and only just set. This version uses a baked lemon cream of eggs, sugar, lemon juice and a little heavy cream. It is poured into a fully baked shell and set in a low oven, so the surface stays glossy and pale yellow instead of puffing or browning.

The two decisions that matter most are baking the shell all the way before it meets the filling and pulling the tart while the center still wobbles. An underbaked shell turns soft under a wet custard, and an overbaked filling cracks and tastes eggy. Squeeze the lemons yourself; bottled juice tastes flat and slightly bitter once baked.

Ingredients

• Sweet almond shell190 g (1½ cups, spooned and leveled) all-purpose flour
• 25 g (¼ cup) almond flour
• 80 g (⅔ cup) powdered sugar
• ¼ tsp fine salt
• 110 g (½ cup minus 1 tsp) unsalted butter — cool, cut into small cubes
• 1 large (about 50 g) egg — beaten; reserve 1 tbsp for sealing the shell
• Lemon filling4 large eggs — room temperature
• 150 g (¾ cup) granulated sugar
• 2 lemons, finely zested
• 120 ml (½ cup) fresh lemon juice — from 3 to 4 lemons, strained
• 120 ml (½ cup) heavy cream

Method

1. Pulse the flour, almond flour, powdered sugar and salt in a food processor. Add the butter and pulse until the mixture looks like damp sand with no visible lumps of butter.
2. Add all but 1 tablespoon of the beaten egg and pulse just until the dough starts to clump. Press it into a flat disc, wrap it and refrigerate for 1 hour, until firm but not hard.
3. Roll the dough between two sheets of parchment to a 30 cm (12 in) round about 3 mm (⅛ in) thick. Ease it into the tart pan, press it into the flutes and trim the top flush. Prick the base with a fork and freeze or chill the lined pan for 30 minutes.
4. Heat the oven to 175°C (350°F). Line the cold shell with parchment, fill it to the rim with weights and bake on a baking sheet for 20 minutes. Remove the weights and bake 10 to 12 minutes more, until the base is dry and evenly golden.
5. Brush the inside of the hot shell with the reserved egg and return it to the oven for 2 minutes to seal it. Lower the oven to 150°C (300°F) and let the shell cool while you mix the filling.
6. Whisk the eggs, sugar and lemon zest until smooth but not foamy. Whisk in the lemon juice, then the cream. Strain into a jug and let it stand for 5 minutes, then skim off any foam.
7. Set the shell, still on its baking sheet, on the oven rack and pour in the filling to just below the rim. Bake for 20 to 25 minutes, until the edge is set and the center 5 cm (2 in) still wobbles like gelatin when you nudge the pan.
8. Cool the tart on a rack for 1 hour, then refrigerate for at least 2 hours. Remove the ring and slice with a hot, dry knife.

Tips for success

• Fill the shell on the oven rack rather than carrying a brimming tart across the kitchen; spills under the crust glue it to the pan.
• A gentle whisk matters. Air beaten into the filling rises to the top and bakes into a dull, bubbly skin.
• For a bruléed finish, sift a thin layer of granulated sugar over the chilled tart and caramelize it with a torch just before serving.

Substitutions

Almond flour

Replace it with the same weight of all-purpose flour. The shell is slightly firmer and less rich but still crisp.

Heavy cream

Crème fraîche at the same volume adds a gentle tang and a slightly richer set. Whole milk works but makes a thinner, less creamy filling.

Lemons

Meyer lemons make a sweeter, more floral tart; reduce the sugar to 120 g. Half lime juice gives a sharper, greener flavor.

Variations

Lemon meringue tartlets

Bake the dough in eight 10 cm (4 in) tartlet pans for 14 to 16 minutes, fill, bake 12 to 15 minutes and top with toasted Swiss meringue.

Lemon and raspberry

Scatter 100 g fresh raspberries over the sealed shell before pouring in the filling.

Troubleshooting

The filling cracked or looks curdled

It overbaked or the oven ran hot. Check the temperature with an oven thermometer and pull the tart while a wide circle in the middle still jiggles.

The crust shrank down the sides

The dough was stretched into the pan or not chilled before baking. Lift and drop the dough into the corners instead of pulling it, and bake it straight from the freezer.

The base is soft under the filling

The shell was not baked until golden or was not sealed. Bake it until the bottom has color, and always brush it with egg before filling.

Bubbles and foam on the surface

The filling was whisked too hard. Let it rest and skim it, or pop bubbles with a kitchen torch held well above the surface right after pouring.

Storage

Keep the tart covered in the refrigerator and eat it within 3 days; the crust softens a little each day. Do not leave it at room temperature for more than 2 hours. The baked, unfilled shell keeps airtight for 2 days at room temperature. Freezing makes the filling weep, so avoid it.

Safety notes

Do not taste the raw dough or the uncooked filling; both contain raw egg, and the dough contains raw flour. Contains wheat, egg, milk and tree nuts (almond).