Katy Perry, John Mayer Kiss Onstage: Watch Their Live 'Who You Love' Duet

Perry joined Mayer in Brooklyn on the last date of his U.S. tour.

John Mayer and Katy Perry turned Brooklyn into their very own paradise valley on Tuesday night. Perry joined her boyfriend onstage at the Barclays Center for the last date on Mayer's 2013 tour as they performed their romantic duet "Who You Love."

In footage posted online, Mayer introduced his girl as "the fantastic Miss Katy Perry." Hitting the stage in a body-hugging dress, Perry gave Mayer a quick kiss before she took to the mic. The couple exchanged loving glances during the duet and even got the crowd to sing along to the Paradise Valley single.

Their performance came hot on the heels of the song's video, which features the couple snuggling and riding a mechanical bull. The couple sat down together on "Good Morning America" Tuesday, debuting the Sophie Muller-directed visual and revealing how the duet came together.

"I had this little chorus for years and it was 'You love, who you love.' I thought that was always going to be a great thing someday. And then it came out again and sometimes you have to play stuff for people; it's really nice to have an unbiased ear," John recalled. "And then [producer Don Was] said, 'Why don't you get Katy to do it?'

"My very first thought was 'You can't do that.' The more I thought about just the music part of it, it made sense. Even if I didn't know Katy, it would have made perfect sense," he continued. "I went in the other room, called her phone."

During the sit-down, Perry dished on what she and her Grammy-winning beau did on their first date. "We just went to dinner, like a regular couple," she said. "We share music as a love together. That's like a common interest."