Tarte au citron meringuée

Make the sweet pastry. Rub the butter into the dry ingredients, add the measured egg and bring the pastry together without prolonged kneading. The pastry forms a smooth disc with no dry flour and is not elastic or greasy. Short mixing keeps the baked shell crisp and tender. Keep the remaining eggs and whites refrigerated until needed.

Chill the pastry. Flatten the dough into a disc, wrap it and refrigerate for 1 hour. The pastry is firm enough to roll cleanly without sticking or smearing butter. Chilling relaxes gluten and firms the butter. Keep the egg-rich pastry cold.

Blind-bake the shell. Roll the cold pastry to 3 mm, line the ring and blind-bake until the base is dry and golden. The shell is evenly golden, dry on the base and firm at the rim. A fully baked shell resists the moisture of the lemon curd. Use oven gloves when handling the hot ring and baking weights. Keep the oven at 180 °C.

Cool the shell. Move the shell to a rack and leave it until no warmth remains. The shell is completely cool and crisp to a light touch. A cool shell prevents the butter-rich curd from softening the pastry immediately. Keep the shell in a clean area while it cools.

Cook the lemon curd. Whisk the eggs, sugar and cornstarch first, then add lemon juice and zest; cook with constant stirring until thick and 82 °C before blending in the butter off the heat. The curd reaches 82 °C, thickens enough to leave a clear whisk trail, and looks glossy after the butter is incorporated. The higher-than-minimum egg temperature gives a stable curd while keeping the lemon flavour bright. Beware hot acidic steam and stir continuously to avoid scorching or curdling.

Chill the filled tart. Fill the cool shell with the hot curd, smooth the surface and refrigerate until fully set. The lemon layer is cold, firm to a gentle touch and does not ripple when the tart is moved. A fully chilled curd supports the meringue cleanly. Refrigerate at 4 °C or below.

Make the Italian meringue. Cook the sugar syrup precisely, start the pasteurized whites before the syrup is ready, then stream the 118 °C syrup into the moving whites and whip until glossy and firm. The syrup reaches 118 °C and the finished meringue is thick, glossy and forms firm peaks while the bowl has cooled noticeably. Hot syrup creates a stable Italian meringue; pasteurized whites add a safety margin. Boiling sugar causes severe burns: pour in a thin stream down the side of the bowl and keep hands clear of splashes.

Brown the meringue. Cover the cold lemon layer with meringue and place it under a hot grill only long enough to toast the peaks. The meringue has an even toasted surface with pale-gold peaks and no blackened patches. Brief top heat colours the meringue without reheating the curd deeply. Watch continuously under the grill because sugar browns quickly.

Set before slicing. Chill the decorated tart for another hour before cutting with a clean hot knife. The tart is cold throughout, the curd cuts cleanly and the meringue stays attached to the lemon layer. A final chill gives the cleanest slices. Keep at 4 °C or below and return leftovers to the refrigerator promptly.