Not my photos.
Some friends in the Amazon recently discovered a new native fruit growing near their place, and they are now planting it in their food forest. The fruits that they found were already damaged, but the one shown in the thumbnail photo was mostly okay, and they said that the flavour reminded them of sapodilla (Manilkara zapota) and mango. The outer layer of pulp is sweeter than the segments around the seeds.
Immediately after ripening the fruits, the tree is flowering again, which is very fortunate for ID purposes.
I'd say that it's Porcelia mediocris based on the photos. Those flowers are clearly Annonaceae, and the shape of the fruit resembles other Porcelia fruits that I've seen. I arrived at the ID using these sources:
Can anyone confirm? Does anyone think that it's something else?
Interesting. Has some characteristics shared with Asimina triloba.
Family resemblance!