The country music star sits with the "Never Worn White" singer on the judging panel of the U.S. TV singing competition, and has said it's "amazing" to watch Katy fawn over her five-month-old daughter Daisy Dove, who she shares with fiance Orlando Bloom.
"It's just really amazing being there with Katy and watching her (be a mom)," he told People magazine. "Sometimes in the breaks, she'll FaceTime Orlando and little Daisy Dove. And so, I'll get to say, 'Hey.' But just watching Katy embrace being a mother is a very beautiful thing to watch. I never had a doubt she would be a tremendous mother."
The musician also praised his friend for being a "trouper" and a "rockstar" for showing up for work despite having a long night nursing her daughter.
"She'd come on set; she would've been up nursing all night. Katy's in the full swing of things with nursing, so we've had to work around her schedule," he added. "But she's been a trouper and showing up and working like she always does. I know she's doing it on minimal sleep, so she's a rockstar."
Luke's kind words come after Katy took to Twitter in September (20) to share a series of messages on her experience of getting back to work whilst raising her baby girl, who was a matter of weeks old at the time.
She wrote, "Popular misconception: being a mom isn't a full-time job."
"Part 2: when a mom finally goes back to work (whatever profession they do) it's not like they been coming from months of 'time off …' she's coming from a full time job … of being a mom, lol."
"Part 3: call your mom and tell her you love and appreciate her and advocate for paid family leave! (sic)"