It seems to be a prehistoric fruit as many things in the tropics (somebody said presidents?). It is a delicous fruit and the only way to eat it, it´s with your hands. In this photo you see some small Zapotes.
Its latin name is "Quararibea cordata" and it is a brown, round and flattened fruit with a sweet, juicy orange pulp. Fruit is highly esteemed in some areas, and rarely known outside of South America.