John Mayer and Katy Perry
06/25/2013 AT 10:05 AM EDT
and John Mayer
's on-again, off-again romance appears to be back on.
After recently telling Vogue magazine
that she was "still madly in love" with Mayer, Perry was spotted out with the "Paper Doll"
singer at New York's Greenwich Hotel on Saturday night and, later, at Monday's Friars Foundation Annual Applause Awards Gala honoring Don Rickles at the Waldorf-Astoria.
At the event, Mayer performed a tune made famous by Frank Sinatra, which captivated Perry.
"When John performed, Katy was enamored by his performance," a source tells PEOPLE. "He sang 'One for My Baby (and One More for the Road).' When they were sitting down, she had her arm around John at one point. They shared kisses."
But the signs of affection didn't end there – Perry and Mayer "were seen smooching and rubbing one another’s backs. They were affectionate towards one another – very lovey-dovey," says another onlooker.
At the end of the evening, Perry – wearing a peach-colored Sally LaPointe dress and Etro necklace – and Mayer were photographed exiting the Waldorf Astoria together.
Natalie Cole and Diana Krall also performed at the event, while other guests included Robert De Niro
, Joan Rivers
, Louis CK, Lewis Black and John Stamos
– Carlos Greer & Raha Lewis