In article .com,
Totty writes

I first came across it in Portugal back in 1966, then didn't come
across it again until came here to the Costa Blanca. I think it is a
type of medlar - I know it is grafted onto quince, and the latin name
is Mespilus Germanica L. and it belongs to the rose family. If you put
the word 'nispero' into an image search engine you will get an idea. I
use it to make chutney, as it is the one fruit that I can't eat raw. It
is very sweet, but at the same time acidic.

Medlar is Mespilus germanica.

Googling suggests that nispero is often used for 'japanese medlar' ie
loquat, Eriobotrya japonica, but that's presumably not the one you mean.
--
Kay
"Do not insult the crocodile until you have crossed the river"