Match report: Manchester United 3 Norwich City 2
Our number seven scored two goals in the first half and a bullet free kick in the second half to see off a valiant challenge from the East Anglians, who are on the verge of being relegated from the Premier League.
In the Easter heat, Ronaldo put us 2-0 up after half an hour, but a Kieran Dowell strike late in the first half and another from Teemu Pikku early in the second drew Norwich level.
But it was Ronaldo who had the ultimate word, scoring in the 76th minute with a thunderous set piece to win his second match ball in less than a month, following a treble against Spurs in March.
It was a scary but ultimately crucial three points for the Reds on a day that saw top-four rivals Spurs and Arsenal lose.
Both teams had a bustling start, with Teemu Pukki having a decent attempt saved by David De Gea, Elanga conjuring up an overhead kick that Tim Krul held, and Ronaldo having a shot stopped.
United were almost awarded the opener after just seven minutes, punishing Norwich's suicidal slapdash play as the Canaries sought to play out from the back.
When defender Ben Gibson got the ball in the box, Elanga was acutely aware of the nerve-wracking position. The Swede effortlessly picked Gibson's pocket and squared it for Ronaldo's easy right-footed finish.
Norwich never seemed at ease on the Old Trafford stage, and the early goal put the Reds up for a possible afternoon nap.
The speed did drop for a period, and despite Norwich never posing a threat, United needed to rekindle their passion.
In the 32nd minute, it was Ronaldo who accomplished it once more.
Jesse Lingard's close-range attempt deflected off goalkeeper Tim Krul for a corner, and Alex Telles sent the resulting set piece to the near post. Ronaldo attacked the ball on the eight yard line and headed it in to give United a two-goal lead.
When Ronaldo attempted a magnificent bicycle kick in the 39th minute, the crowd erupted in applause, but our No. 7 sent his party piece flying high into the East Stand.
United, on the other hand, failed to put the Canaries away in the first half, and they clawed a goal back.
A rare Canaries assault saw Dimitris Giannoulis find Pukki, whose cross to the back post was met by a strong header by the unmarked Kieran Dowell, taking the sting out of what should have been a saunter in the first half.
Norwich's late first-half goal was not the consolation most at Old Trafford had hoped for, as the visitors leveled the game seven minutes into the second half.
In the opening stages, United appeared in command again, but when Dowell slipped Pukki in behind the Reds' defensive line, the Norwich striker made no mistake in converting with a low right-footed shot that deflected off De Gea's post.
Although a VAR assessment for offside against the Finnish striker was delayed, the goal was awarded.
United were stunned, and it required a stretched arm from David De Gea to stop a goal-bound low drive from Milot Rashica wide of his post four minutes later.
On the hour, the Telles-Ronaldo corner combination nearly put us back in front, but our talisman's header was fierce but straight at Krul.
Norwich's confidence was high, and midfielder Dowell, who had already scored and assisted, tried a long-range chip that barely cleared De Gea's bar.
Rangnick replaced Jesse Lingard with defensive midfielder Nemanja Matic after 63 minutes due to United's vulnerability on the counter.
After Norwich had a stranglehold on chances, the interim manager tried again to add creativity and danger by replacing Pogba and Telles with Marcus Rashford and Juan Mata 10 minutes later. But it was Ronaldo who ultimately made the difference.
After 76 minutes, a venomous 30-yard free kick arrowed home in front of the Stretford End, brilliantly putting United back in ahead and securing the Portuguese striker another another match ball.
After a see-saw of emotions, Fernandes fired in a low stinger after 82 minutes that deflected wide off Krul's knee, and we were able to see the match out reasonably easily.
United: De Gea, Dalot, Lindelof, Maguire (C), Telles (Mata 73), Lingard (Matic 63), Pogba (Rashford 73), Sancho, Fernandes, Elanga, Ronaldo.
Subs not used: Henderson, Wan-Bissaka, Bailly, Jones, Hannibal, Garnacho.
Goals: Ronaldo (7, 32, 76)
Norwich City: Krul, Byram, Gibson, Hanley, (C), Giannoulis, Dowell (Placheta 73), Normann, Rashica, Lees-Melou (Rowe 81), McLean (McLean 73), Pukki.
Subs not used: Gunn, Aarons, Zimmermann, Rupp, Tzolis, Sorensen.
Goals: Dowell (45), Pukki (52)