It was the first treble in the opening fixture of the season for the club since MUTV favourite Lou Macari in 1977 against Birmingham City.
The Portuguese Magnifico's first goal of the afternoon came in the 30th minute after latching on to a through ball from Paul Pogba on the edge of the penalty area, before firing past Illan Meslier.
Bruno's second arrived 10 minutes after half-time as he evaded Junior Firpo with a clever turn inside the penalty area to make space for a shot, which looked to have been cleared off the line, but referee Paul Tierney awarded the goal after consulting his watch.