Lemon curd is very popular in America and Britain. The recipe for the curd is simple, it is a kind of classic. It is used on toast, in various tarts, pastries, as an addition to cream, etc. Essentially, it is a custard based on fruit juice. This curd can be made using orange, mandarin, or grapefruit juice, but then the taste will not be as bright. You can mix lemon and orange juice and the curd will be less sour.