can't take your eyes off someone/something

can't take (one's) eyes off (of) (someone or something)

Cannot stop looking at someone or something because it is so beautiful, visually pleasing, interesting, etc. Your little girl is so adorable—I just can't take my eyes off of her! The juxtaposition of colors in that painting is so strange that you can't take your eyes off it.
See also: eye, off, take
Farlex Dictionary of Idioms.

can't take your eyes off someone/something

or

can't keep your eyes off someone/something

COMMON If you can't take your eyes off someone or something, or can't keep your eyes off them, you want to keep looking at them, usually because they are so beautiful. Anne looked so beautiful no one could take their eyes off her. I'd never seen a diamond that size and couldn't take my eyes off it. We just couldn't keep our eyes off each other from the first time we met.
See also: eye, off, someone, something, take
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • can't keep (one's) eyes off (of) (someone or something)
  • can't take (one's) eyes off (of) (someone or something)
  • be (not) a pretty sight
  • be as cute as a button
  • drop-dead gorgeous
  • be/look a picture
  • cute as a button
  • (as) cute as a button
  • spiff up
  • spiffed up