Cher found a way to turn back time ... making a surprise visit to the home she once shared with Sonny Bono ... 49 years after she was last there.
We're told Cher made an unannounced stop at her old digs off Laurel Canyon Drive in the Hollywood Hills -- where she and Sonny lived from 1964 to '65 ... just as they were hitting it big.
Kind of a bummer for the homeowner, Daniel Dreifuss ... who wasn't home at the time. Dreifuss tells TMZ, his roommate answered the door and got the shock of his life when he saw Cher and her 2 assistants.
We're told she came in and had a look around and was "down to earth and super sweet." But the tour came to an abrupt stop at her old bedroom ... because another housemate was asleep inside the room and couldn't be disturbed. Even for Cher.
Dreifuss says he hopes to make amends by inviting her back for another visit.