The two act very much the couple at the afterparty for Mayer's Madison Square Garden concert

By KC Baker Michelle Hainer
March 01, 2007 11:50 AM

Wrapping up his Continuum tour, John Mayer starred solo at a sold-out Madison Square Garden show Wednesday night, but when it came to the afterparty at Stereo, he conspicuously shared the spotlight with Jessica Simpson.

Acting very much like an affectionate couple, Mayer and Simpson entered the club holding hands, with a bouncing Simpson pulling her beau along to the VIP area, where they settled in with his arm around her between bouts of talking and kissing.

Not that they sat still. At one point while standing on top of the banquette, Mayer rocked to David Bowie’s “Let’s Dance.” And when Beyoncé’s “Crazy In Love” came on, Simpson got up and danced, too.

Simpson, 26, and Mayer, 29, have been spotted out together for months, including stops in Miami, New York and Los Angeles, but as of yet have remained relatively mum about their relationship. Though just last week, when asked about the romance, Mayer told Time Out New York, “I don’t think I ever denied it.”

At his concert, Mayer thanked his parents, who were in the audience, as well as fans for their support. “It’s all because of you,” he said of his success, adding later, “For everything that sucks in life, there’s something that helps recover it.”

Simpson was also at the show, watching from the soundboard, a source close to Mayer tells PEOPLE.

Backstage after the show, “executives from his [Mayer’s] label presented him with two cakes from custom cake designer Sugar Couture, in the shape of the two Grammys he just won,” a source close to Mayer tells PEOPLE. “It was a big celebration because that was his first night back in New York City since winning the Grammys.”

Also backstage with Mayer was Alicia Keys, who had made a surprise appearance during Mayer’s concert – then later showed up at Stereo for the afterparty.

At the club, Mayer and Keys both danced on top of the banquette, singing along to Michael Jackson’s “The Way You Make Me Feel” and then “Don’t Stop ‘Til You Get Enough.”

Later, when Justin Timberlake’s “SexyBack” came on, Simpson, who is also in New York to shoot scenes for her movie Blonde Ambition, danced in front of Mayer with her back to him – and also danced with friends.

When it came time to go, Mayer and Simpson huddled close together, and he kissed as they made their way out of the club.