I had originally posted this to Reddit but the mods removed it and suggested I take it to a rock and minerals subreddit.... which was infuriating. Anyways, this came in a collection of other Mexican arts and pottery. I have not found anything exactly like it online. I actually have a pair of them. I thought it might be for tortillas but it seems small. It's abou 4" across. Any help is appreciated.
it reminds me a bit of a stone tortilliero, but it's not as deep as they usually are. a tortillero is a round shaped container which helps keep tortillas warm during a meal. it usually has a lid, too.
What about a tortilla press? Put dough in it, place a flat rock on top, and now you got a tortilla.