Citron
A source of confusion is that "citron" or similar words in French (and other languages), and English are false friends, as they refer to the lemon. Indeed, into the 16th century, the English name "citron" included the lemon and perhaps the lime as well.
Bichon au citron
The bichon au citron is a French pastry. It is similar to a turnover in size, shape, and that it is made of puff pastry. A major distinguishing feature is that it is filled with lemon curd. The outer layer of sugar is sometimes partially caramelized.