Singer Carrie Underwood's 2013 Primetime Emmy Award performance was the most-tweeted about moment of the ceremony. The hitmaker performed Yesterday during Sunday's (22Sep13) telecast to commemorate the 50th anniversary of The Beatles' first appearance on U.S. TV show The Ed Sullivan Show - and the death of President John F. Kennedy. The tribute generated 17,090 tweets per minute, according to the Los Angeles Times. The singer performed the beloved song after she received a letter from Sir Paul McCartney giving her permission to cover the track. On Sunday (22Sep13), she wrote on Twitter.com, "The coolest thing about singing Yesterday on the #Emmys is the sweet letter I got from @PaulMcCartney giving me his blessing to sing it!"