Victory for Jose Mourinho's men opened up a five-point lead on Liverpool in the race for second and edges United ever closer to guaranteeing a top-four finish.
However, they had to endure a nervy finish as Eric Bailly's own goal brought Liverpool back into the game 24 minutes from time.
Here, AFP Sports looks at three things we learned from the latest meeting between English football's two most successful clubs.
Rashford deserves a run
We'll never know whether a late injury to Paul Pogba in training on Friday is why Rashford was handed his first league start of the year.
What is for sure is that Rashford showed what United have not been getting from Alexis Sanchez since his January move from Arsenal that has seen Rashford slip down the pecking order.
With Sanchez operating in a more central role vacated by Pogba's absence, Rashford tore down the left to leave Trent Alexander-Arnold in a daze and Liverpool quickly 2-0 down.
Even if Pogba does return for Tuesday's crucial Champions League clash with Sevilla, Rashford has surely down enough to ensure he for once isn't the man sacrificed.
Lukaku exposes Lovren
Whilst Rashford applied the finishing touch for United's quickfire double, Romelu Lukaku had a huge part to play in the creation of both goals.
On both occasions the Belgian bullied Dejan Lovren to win long balls forward.
It is far from the first time Lovren has been found wanting and questions must be asked how much of a defensive overhaul even £75 million club record signing Virgil Van Dijk can inspire with the Croatian alongside him.
For all of Liverpool's improvement at the back since Van Dijk's arrival in January, they have now conceded 20 goals in nine games against top six opposition this season.
Mourinho stops Salah and Co.
Liverpool enjoyed the lion's share of possession throughout, yet barely created a clear-cut chance for free-scoring front three Mohamed Salah, Sadio Mane or Roberto Firmino.
When United's back line was finally breached it came via their own player when Bailly miscued a Mane cross into his own net.
Mourinho has often been criticised for his defensive tactics and there were boos at his decision to sacrifice Rashford for the physicality of Marouane Felliani 20 minutes from time.
However, the midfield screen of Felliani, Nemanja Matic and Scott McTominay in front of United's back four crowded out the trio that have combined for 68 goals this season.