"He knows me. He f-cking knows me," the rapper says.
The "Bodak Yellow" rapper took to Instagram to freak out over the letter in front of her followers, and like most of Cardi's videos, it's joyous entertainment.
"He said I'm the biggest thing in Ireland," she said while clutching the note. "Bitch this is f-cking Bono. He knows me. He f-cking knows me, bitch. I can't believe it. I can't motherf-cking believe it. Nobody talk to me now."
Although the letter was hardly legible, the legendary performer's signature is clear on the paper.
Cardi B later thanked Bruno Mars on Instagram for the opportunity to perform their hit "Finesse" on the Grammy stage.
"I want to thank you so much. I don't even know how," she wrote. "Maybe one day you'll need a kidney. I got you. Congrats on your wins tonight. You deserve it. You sing, dance, play instruments, produce your videos SHIT you probably know how to build a house, You ARE AMAZING and you gave me rhythm."