This is the flower from the tree that forms the "fruit".
And this is the "fruit". The inside is supposed to be edible but I couldn't find anybody that had ever actually eaten the fruit.
What's the name of this really weird tree?
It's a "cannonball tree". Really, that's the actual name! I can see where they could get the name. The fruit grows to about the same size as a "standard" ship cannon ball.