apple of

the apple of (one's) eye

A cherished or favored person. This phrase is thought to be Biblical in origin. My nephew is just the apple of my eye. He has five kids, but his only daughter is clearly the apple of his eye.
See also: apple, eye, of
Farlex Dictionary of Idioms.

apple of (someone's eye)

Fig. someone's favorite person or thing; a boyfriend or a girlfriend. Tom is the apple of Mary's eye. She thinks he's the greatest. John's new car is the apple of his eye.
See also: apple, of
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • apple of eye
  • apple of my eye
  • apple of one's eye
  • the apple of (one's) eye
  • the apple of somebody's eye
  • the apple of your eye
  • corn in Egypt
  • get thee behind me
  • millstone
  • nether
References in classic literature
And he won't let a soul but a Dalmatian pick a single apple of all those apples.
The Valley of the Moon
Two Poets were quarrelling for the Apple of Discord and the Bone of Contention, for they were very hungry.
Fantastic Fables
"The fatal apple of Eden couldn't have had a rarer flavor," commented Anne.
Anne of The Island
My most favorite apple of all time has a snow-white flesh and is supercrisp and juicy.
The adaptable apple. (In Profile)