Lukaku converted the spot-kick as monkey chanting was heard inside the Sardegna Arena. The Belgian then stared down his abusers, before being embraced by his Inter teammates.
Inter, who had initially taken a first half lead in Sardinia through Lautaro Martinez before being pegged back soon after half-time, held on to their advantage the second time to win 2-1.
Sadly, Lukaku is the latest in a growing list of players to suffer racial abuse at the hands of Cagliari supporters in recent years.
Now with Everton, Moise Kean suffered similar abuse while playing against Cagliari for Juventus last season. Juve midfielder Blaise Matuidi was racially abused by Cagliari fans a year earlier, but no action was taken by Italy’s football authorities.
Action was taken when former Portsmouth and Inter star Sulley Muntari was racially abused while playing for Pescara against Cagliari in 2017, but against the Ghanaian himself.
Muntari was shown a yellow card for dissent when he complained to the referee about the abuse from the stands and subsequently walked off the pitch in protest. He was shown another yellow card as a result, leading to a red, and the associated one-match ban was later upheld.
Going back to October 2010, former Inter striker Samuel Eto’o was also subjected to racial abuse in Cagliari, a game in which he scored the only goal for the then European champions.
Lukaku’s winning goal means that Inter are top of Serie A after two rounds of fixtures, leading reigning champions Juventus on goal difference at this early stage. Lukaku himself has already scored two goals since sealing a £73m transfer from Manchester United.
Fellow new arrival Alexis Sanchez was included on the bench for the game, but he remained an unused substitute and so will have to wait for his Inter debut.