I thought these were apples. Came across them at a farmer's equity stall at the cultural market being hosted by the 53APFF here in Kaohsiung Taiwan. I sampled a slice and it had the texture of a yellow chinese pear like you would get at a Malaysian supermarket, but tasted caramelly, very sweet and lusciously refreshing.
Turns out it has a stone in the middle instead of seeds, so it's some sort of plum I guess. Yummy.