updated 03/07/2012 AT 1:00 PM ET
•originally published 03/07/2012 AT 1:30 PM ET
The starlet had the support of her mom’s ex husband during her four-song performance Tuesday at Hollywood’s Sayers Club Sessions Presented by Jason Scoppa. (Moore, who recently returned to Los Angeles after treatment did not attend – nor did dad Bruce Willis.)
Rumer, who recently showed off her vocal prowess at the club, didn’t seem nervous at all before her performance, according to an onlooker, and she greeted Kutcher as he arrived with a friend after midnight.
According to the onlooker, the Two and a Half Men star attempted to keep a low profile, letting Willis, who recently premiered The Diary of Preston Plummer in Miami, bask in the spotlight instead.
And as soon as Rumer, 23, took the stage, Ashton looked on proudly and snapped some photos on his phone.
As for her set, Willis tackled Ann Peebles’s soul staple “I Can’t Stand the Rain;”“High Low Middle” by indie chamber pop outfit My Brightest Diamond; Otis Redding’s “(Sittin’ On) The Dock of the Bay”; and British soul singer Lianne La Havas’s “Age.”
As her performance continued, the crowd got more into it, clapping along and encouraging her. Kutcher whistled at one point and even sang along to some of the lyrics.
After the show, Willis talked to a few people before sharing a long, emotional embrace with Kutcher.
Says the onlooker: “It seemed really happy and loving – and like the two would be friendly … no matter what.”