They are called limoon aswad (black lemon) or loomi and are used heavily in Gulf Arabic and also Iraqi cuisine. I have never heard of them being used outside of this region...(Moroccoans use wet salt preserved lemons), as far as I know.
You can use them in Gulf Arab watery tomato meat curries called "marag" or "salona", but be careful and don't go crazy with them because they can add a strong bitter flavor in addition to sourness. Gulf Arabic food is surprisingly similar to North Indian-Pakistani food in many ways in terms of the rice and curry factor, and very unlike the Arabic foods from other regions---but dried lemon is not used in South Asian cooking BTW. Black lemon are also used to flavor some very typical Gulf Arab soups. You serve Gulf Arabic curries with basmati rice (Gulf Arabs as well as Iraqis use Indo-Pak basmati) or with Iranian style flatbread or a thin naan...hmmm, it occurs to me that Iranians may use these dried lemons as well, but I am less familiar with Persian cuisine.
Anyhow, I googled you a Gulf Arab chicken stew recipe that contains dried lemons. It also calls for "bezar" or bizaar which is basically the same thing as Indian garam masala, just in case you actually try to make this:
The recipe looks pretty spot on. Enjoy your dried lemons.
I spent the Summer in Israel (joelsummer08.blogspot) and while I was there I tried some dried lemons at the home of an Israeli who was born in Iran.
She made them in a meatball stew. I went to the shuk that week and bought a bag of them.
Now that I am home, I have put them in a vegetarian version of the stew using veggie meat balls and the usual variety of stew contents.
I also included them in a ratatouille that came out really good.