The Portugal forward met Leonardo Spinazzola’s cross with a towering header with six minutes left.
Sasa Lukic’s low shot after a Miralem Pjanic error had given Torino hope of a memorable victory against their rivals.
But they can take consolation from the fact this point takes them to 57 – equalling their Serie A record.
The draw means they stay sixth, two points behind fourth-placed Atalanta in the battle for Champions League qualification with three games to play.
The match was brought forward a day to avoid clashing with Saturday’s 70th anniversary of the air disaster that wiped out the “Grande Torino” team of the 1940s.