With increasing pressure on their position as the PL pacesetters, Liverpool made a slow start in the capital and were fortunate not to be behind inside five minutes when Mikkel Damsgaard failed to connect with Mads Roerslev’s low cross.
The Dane had the goal at his mercy, which is more than can be said for Ryan Gravenberch when he let fly from range, forcing Brentford goalkeeper and international teammate Mark Flekken into a smart save.
Dominik Szoboszlai came even closer when he rifled an effort against the crossbar, while Christian Nørgaard headed over for the Bees from a Bryan Mbeumo free-kick.
Arne Slot’s men made most of the running before the break, but there was no way through in the first half as Flekken rushed off his line to smother a Cody Gakpo effort.
The Reds’ dominance continued into the second half as their corner tally reached double figures, but Brentford’s rearguard continued to stand strong.
Luis Díaz’s low drive forced Flekken into another stop, moments before being replaced by Núñez, who headed wide soon after coming off the bench.
As the contest entered its closing stages, chances started to flow at both ends with Alexis Mac Allister heading wide for the visitors before Alisson pawed Mbeumo’s free-kick away and denied a low drive from the Cameroonian.
Liverpool’s growing frustration became evident when Trent Alexander-Arnold unleashed from long-range, but the full-back’s impressive effort provided more than a scare to the home support when it whistled past the post.
The Reds kept coming, with Mohamed Salah firing wide before the decisive strike came at the death.
A second consecutive Liverpool goal to arrive from a substitute striker, Núñez slotted home from close range after being found by Alexander-Arnold.
The Uruguayan struck again just two minutes later, applying a composed finish from Harvey Elliott’s lay-off to extend their unbeaten away run to 11 league matches.
Late heartbreak for Brentford meanwhile, who’ve won just one of their last nine matches and none of their past five on home soil.