Marc Anthony seems to be moving on from Jennifer Lopez. Four months after their split, he was with a mystery “beautiful blonde” as his date at a recent dinner celebrating the nuptials of Martha Stewart Living Omnimedia honcho Charles Koppelman and Gerri Kyhill. Also at the 583 Park Ave. bash for the onetime EMI North America CEO and his bride were Frederic Fekkai, David Steinberg, Allen and Deborah Grubman and finance guru Lauren Krueger.