Those efforts are in sharp contrast to his form with the national team, for which he has scored only once in seven games despite being such a consistent performer at club level.
Victor Ikpeba, a former African Player of the year who has been in a similar situation, says Nigerians -- and the Super Eagles coaches -- must be patient with Onuachu.
"It is not easy to come into the national team and make an impact," Ikpeba told ESPN.
"Even Yekini did not make an immediate impact."
Onuachu opened the scoring for Racing Genk as they went on to win 2-1 at home to Sporting Charleroi in the Belgian Jupiler League at the weekend, taking his tally to eight goals in as many league games for the season.
A little more unpacking shows he has scored seven goals in his past five club games -- with goals in five straight games, including two braces. For a season that is still only eight games old, that is a remarkable piece of marksmanship and he is just one goal shy of his league tally from last season.
Indeed, Onuachu has improved his scoring record steadily since he tallied six goals in 25 (mostly substitute) appearances for Denmark's FC Midtjylland in the 2015/2016 season.
Trusted with 29 starts the following season, he scored 18 goals in 36 games; that tally dropped to 10 goals the next season, but he improved to 17 the season after that.
It was on the back of those performances that Genk moved for him last season, and the Nigerian repaid them with nine goals. He is already on pace to eclipse that tally with this season barely underway.
He was called up to Nigeria's senior squad on the back of those efforts, and he scored a sweetly struck volley from range on debut to propel the Super Eagles to a 1-0 pre-Africa Cup of Nations friendly win over Egypt.
With Odion Ighalo then on the cusp of retirement, Nigerians were quick to jump on Onuachu as a potential replacement.
That was as good as it got for Onuachu in Nigeria colors, however.
He struggled in subsequent games, and the excitement that greeted that first appearance gradually gave way to disappointment and then, predictably, to outright flak before he was left out of post-Afcon squads.
Onuachu was not even selected in the current squad for the latest round of internationals, despite his rush of early goals this season; he was neither in the main squad, nor on the back-up list.
Only a fortuitous set of circumstances, involving positive COVID-19 tests at Napoli, which meant Victor Osimhen was unable to make the squad, and reported pressure on Super Eagles coach Gernot Rohr from the Nigerian football hierarchy, saw Onuachu skip the line ahead of players on the standby list to replace Osimhen.
But once again, on his seventh international appearance, Onuachu failed to deliver in the 1-0 loss to Algeria. The backlash was unforgiving, as was to be expected, and he was dropped for the next game, a 1-1 draw with Tunisia.
It looks for all the world as if his international future may be on a knife edge, especially after Genk teammate Cyriel Dessers made a sharp cameo on debut, running channels, turning defenders and attacking with pace, and seeing a scuffed shot imperil the Tunisian goal.
Dessers, who was in the original squad, certainly seems more likely to be called up for the Afcon qualifying games against Sierra Leone in November.
Incidentally, Dessers is not only behind Onuachu in the Genk pecking order but also has scored only twice this season.
Why is Onuachu scoring with such ease for Genk but not for Nigeria?
He is not a one-dimensional striker despite his towering, beanpole frame, with games at club level having shown that he has dainty footwork, passable hold-up and link-up play, and occasionally drops deep to pick up the ball with the ability to also drift wide to set up teammates.
He can hit a rasping volley -- as he showed against Egypt in Asaba -- with the same ease as he can turn in a tap in, and his positional sense in and around the box is just as good as any.
But he really excels at Genk with his aerial strength; he has scored most of his goals with his head -- no surprise considering he stands at 200 cm (6'7") -- but he has not been able to bring all of that to bear for Nigeria.
He has struggled with his technique and positioning In the games following his debut, and then he did not seem to get much in the way of supply against Algeriaand unlike at club level; in fact, the Super Eagles crossed more balls in the second game against Tunisia (against whom he did not feature) than in the first against Algeria, leading to suggestions that perhaps the team should play more to his strengths.
"There was not serving him the ball well," Ikpeba told ESPN.
"When you have that kind of striker, you have to give him the ball. Our wide players are not crossing the ball; they always want to dribble, and come inside.
"They need to get used to him and keep trying to find him, and they need to cross the ball more to him."
Rohr was quick to shoot that suggestion down, however.
"The team doesn't have to adapt the game to one player Paul Onuachu," Rohr told ESPN.
"He has to adapt to the collective.
"We have our football: We try to find each other with short passes and find the wingers, playing quickly, switching from one side to the other, and he has to integrate with his qualities and to adapt to this."
Illustrating the major playing differences between Genk and Nigeria, the Belgian club side tend to put in more crosses for Onuachu and their pace of play is slower than the Super Eagles'; this means he sees more of the ball, and has more time on it, at club level.
Nigeria's wide forwards also are not wingers and don't play like wingers; they tend to pinch in and attack the defence whereas Onuachu's teammates at Genk tend to hug the sideline and whip the ball in more often.
Rohr did suggest, though, that Onuachu could be an option to escape the press, and also that maybe the wingers would need to cross the ball more.
"We will not change our game only for him, and make long kicks in the air. We will play football. But it can happen under pressing; we can give long ball to him.
"He has to adapt.
"We play on the ground -- we do not want to play all the time in the air -- but our wingers can give good crosses, like you say."
Onuachu is just the latest Nigerian striker who has done well in Europe but failed to establish himself with the Super Eagles.
Richard Owubokiri lived in the international shadow of Rashidi Yekini despite being more recognised at club level with Boavista, for whom he scored 30 goals in one season. Jonathan Akpoborie was lethal in Germany but never could make himself a mainstay in the Super Eagles.
Ikpeba holds the single-season record in goals for a Nigerian in France, and won the African Player of the year Award for his exploits at Monaco, but was never established as a Nigeria mainstay. Peter Ijeh had a big reputation in Sweden but was in and out of the Super Eagles squad.
Ikpeba, who had the most successful international career of the aforementioned players, winning Olympic gold with Nigeria, playing at the World Cup and Africa Cup of Nations, says patience and perseverance are key if a player is to translate club form.
"As far as [Onuachu] is part of the squad, they should keep inviting him. It is always difficult getting the same scoring form from your club to the national team. But he is a good player and we have already seen it. And he is a goalscorer. When the goals will come they will start coming, but it won't come if others don't help him.
"If the coaches believe in him and what he can bring to the team, and they give him more opportunity, he can come good."