The Belgian took his tally to 18 goals in all competitions after scoring twice in a 4-1 Coppa Italia win over Cagliari on Tuesday, once again answering those who said he was not worth the club record 80 million euros ($89.27 million) Inter paid for him at the start of the season.
Fourteen of those goals have come in Serie A, putting him level with Juventus forward Cristiano Ronaldo and behind only Lazio forward Ciro Immobile who has 20.
With Serie A at the halfway mark, Inter, who visit relegation-threatened Lecce on Sunday, are second with 46 points, two behind leaders Juventus who host Parma.
Lazio, third with 42, host Sampdoria on Saturday as they chase an eleventh successive league win.
Lukaku, a powerful 1.90 metre forward, was often singled out for criticism last season and was upset when United manager Ole Gunnar Solskjaer categorised him as a target man. "He's one of the top number nines when you want to play with that kind of striker," said the Norwegian.
"Because of my size, they think that I'm like the traditional big guy," Lukaku replied. "Well, I'm not that type of dude. I need to face the goal, that's when I'm dangerous."
His tally this season includes a goal against Genoa where he collected the ball, skipped past a defender and rifled a shot in off the bar, while against Napoli, he intercepted a pass in his own half and ran 50 metres to score a remarkable solo goal.
In fact, Lukaku has had an impressive scoring record throughout his career which began when he made his debut for Anderlecht at the age of 16.
He scored 42 goals in 96 appearances for United, 87 goals in 166 matches for Everton and 41 in 98 games for Anderlecht while his tally for Belgium is an impressive 52 in 84 games.
Conte, who took over as Inter coach this season, said that he had been an admirer of Lukaku's ever since he coached Chelsea in the English Premier League.
Lukaku, on the other hand, was impressed by Conte's Italy side when they beat Belgium 3-1 at Euro 2016 despite a much weaker squad on paper.
"I heard people say Romelu Lukaku was a donkey," said Conte after the 1-1 draw against Atalanta on Saturday. "I heard all sorts of things, not even that long ago."
"It's easy to speak well of him now, but if we think back to just a few weeks ago....," said Conte.
"I always said Romelu was a rough diamond that needed work to smooth him out. Lautaro Martinez is the same. These lads are 26 and 22-years-old, they are still young... Now, I can get to work on polishing the diamond." ($1 = 0.8961 euros) (Writing by Brian Homewood Editing by Christian Radnedge)