How about Magnolia grandiflora, as the fruit can easily reach the size you described (and larger, to 8" long X 2-3" wide, according to my mom's...
If you are in Singapore, outside is good, east or north exposure. Cyathias (bits in the center) are the true flowers and the red 'petals' are just...
I know this was posted a number of months ago.... but this would be easier confirmed if there were a few more details; Spore print colour? Gill...
