A smooth, intensely tangy preserve made from eggs, butter, sugar, and fresh lemon juice — thicker and richer than jam, with a vivid yellow colour and a clean, bright flavour; used as a spread on toast and scones, a filling for tarts and cakes, and a swirl in cheesecakes and ice cream; requires careful making — the eggs curdle if overheated — but keeps for weeks refrigerated.
Making lemon curd
Lemon curd is made by combining lemon juice, zest, eggs, butter, and sugar in a bowl over barely simmering water (a bain-marie), then stirring continuously until the mixture thickens enough to coat the back of a spoon. The eggs must not overheat or they scramble — the temperature should stay below 82°C. The finished curd is strained to remove zest and any egg strands, then poured into sterilised jars. Well-made lemon curd is silky, bright, and intensely flavoured.
Keeping quality
Home-made lemon curd keeps for 2–3 weeks refrigerated — far shorter than commercially made versions, which contain preservatives. The freshness is a virtue rather than a drawback; a freshly made curd has a vibrancy that commercial versions rarely match. Freezing extends the keeping time. Commercial lemon curd typically uses cornflour as a partial substitute for eggs, extending shelf life but reducing complexity.
The lemon tart
Lemon curd is the filling for lemon tart — one of the most enduringly popular French and British patisserie items. The classic tarte au citron uses a richer, curd-like mixture baked in a pastry case. When the filling is made separately as lemon curd and poured cold into a baked pastry case, it is usually called a lemon curd tart. Both produce the same sharp-sweet contrast between buttery pastry and intensely lemony filling.
Variations
Orange curd, lime curd, and grapefruit curd are all made by the same method. Passion fruit curd — the juice and pulp of passion fruit substituted for lemon — has become particularly popular. Blood orange curd produces a vivid pink-orange colour. All depend on the same basic acid-fat-egg emulsion principle.