Lemon curd is a thick, creamy spread that is made by cooking together lemon juice, egg yolks and sugar. Fresh lemon juice and sugar provide the flavor of the curd, while the egg yolks serve to thicken up the mixture as it cooks, just as eggs thicken up a cooked custard. Most curd recipes also call for butter to be added to the finished curd, just to add a little extra richness and an extra-silky mouthfeel. Lemon curd has a bright, sweet-tart lemon flavor. Other citrus fruits are often used to make variations on lemon curd, but you can also use purees from non-citrus fruits, such as raspberries and strawberries, to make other types of curd.
Lemon curd can be used for a variety of different things. The simplest way to use it is to spread it onto a homemade scone, into a crepe or onto a toasted English muffin. Folding some in to a plain batch of buttercream will make a delicious lemon frosting for a cake, and plain lemon curd can also be used as a filling for a cake, or as a sauce on the side. It can also be incorporated into a variety of recipes, including ice cream and tarts.