PSG host relegation battling Le Havre on Saturday
The 36-year-old striker found the net with a header, a right-footed penalty and a left-foot shot and celebrated by pointing to his ear in an apparent response to recent criticism.
The Italian champions and their Portuguese talisman were under pressure to perform after suffering a disappointing European elimination against Porto on Tuesday.
They enjoyed a comfortable win despite Giovanni Simeone's second half strike for the hosts and are now third with 55 points, 10 behind leaders Inter Milan with a game in hand.
It was Cagliari coach Leonardo Semplici’s first defeat since taking over in February and left his side in 17th place on 22 points, two clear of the relegation zone.