The Uruguay midfielder rescued a point from a largely inept performance from United on Saturday by driving home a shot from the edge of the area eight minutes after Bruno Fernandes started the visitors' fightback at Goodison Park by curling in a free-kick.
United had been on course to slip to a third straight loss — and ninth defeat in 15 league matches since Ruben Amorim took charge in November — after first-half goals by Beto and Abdoulaye Doucoure.
There was a late scare for United when Everton were awarded a penalty for a foul by Harry Maguire in the third minute of stoppage time, but after a video review, the on-field referee changed his initial decision.
Everton faded halfway through the second half and United took advantage, though the comeback will not mask the big problems facing Amorim as he looks to get the fallen English giants up the standings from their current embarrassing position of 15th place.
Amorim's side had struggled for much of the contest, with their former England defender Rio Ferdinand, commentating for TNT Sports, labelling their display as "embarrassing" and "unforgivable" shortly before Fernandes sparked their comeback.
Everton, though, extended their unbeaten run under David Moyes, who returned for a second spell as manager last month, to six league games.
