Hundreds of supporters voiced their anger at the club’s owners, the Glazers, with green-and-gold scarves and banners demanding the sale of the club.
While fans held their anti-Glazer placards aloft as Bruno Fernandes led United out as captain, the supporters were on their feet for a very different reason midway through the first half.
Cavani’s future at the club had been uncertain of late, with United boss Ole Gunnar Solskjaer trying to tempt the striker into signing a new deal with the prospect of playing in front of a packed Old Trafford.
The Uruguayan has put pen to paper with a new one-year deal, and gave the 10,000 fans in attendance a moment of magic to open the scoring.
A long kick from David De Gea was seemingly flicked on by Fernandes, and Cavani duly chipped Alphonse Areola first-time from 40 yards after spotting the Fulham goalkeeper off his line.
The goal sparked an outpuring of emotion as United fans celebrated a stunning goal after so long away – though Fulham could feel hard done by given replays showed Fernandes got little if any contact on the ball, which should have meant that Cavani was offside.