One onlooker tells Life & Style magazine, "During appetisers, Katy used her fork and her hands to eat off her and the others' plates and John fed her with his fork!"
"Katy and John sat across from one another. They seemed relaxed and comfortable. Katy was over-the-moon happy... and laughing a lot. John was just as happy. They were really flirty. They kept leaning into each other over the table to talk."
Perry even documented the night out by asking a waitress to snap a photo of the foursome, just before they left and headed to private club Soho House, where the music lovers were spotted playing pool.
Earlier in the evening, Mayer showed up at Perry's private concert at the Best Buy Theater. And the couple was spotted kissing at Hotel Chantelle the night before.
Mayer and Perry briefly dated earlier this year, although neither has addressed romance rumors.
The couple allegedly broke up in August, but Perry and Mayer were spotted together again at the FYF Fest in Los Angeles on Sept. 1.