Inter stay second within the table, 3 points behind Juve who beat Fiorentina earlier on Sunday.
Christian Eriksen, Ashley Young and on-loan Chelsea winger Victor Moses created their league debuts for the Nerazzurri.
But it absolutely was Lukaku who ensured success, scoring with a close-range shot before adding his second with a penalty.
The former Manchester United forward has currently scored sixteen league goals since moving to Italy last summer and has scored twenty for inter altogether competitions.
He was helped by some poor goalkeeping by the hosts’ Juan Musso for his 1st, then by on-loan United forward Alexis Sanchez for his second – with the Chilean winning the spot-kick from Musso.
Antonio Conte’s side had drawn their 3 previous league games 1-1 . they’re next in action after they host their rivals, AC Milan, within the Milan derby on Sunday, 9 February.