Cardiff Blues weathered a storm to snatch an 11th straight victory over the Dragons thanks to a late try from Teddy Williams.
The homes side were in control at the Arms Park following a fine first half try from Josh Adams try but the Dragons launched a comeback after Owen Lane was red carded and Jason Harries binned.
Sam Davies kept the scoreboard ticking following Rhys Lawrence's try and the visitors led by six going into the final 10 minutes.
But just moments after coming on as a replacement Williams, the son of Arms Park legend Owain Williams, cut an inside line to power over.
Evans was denied an early opportunity to boot his side into the lead, and following an eternity of replays Dragons try-scorer Lawrence was shown red.
But the replacement fly-half showed nerves of steel to slot the decisive points with Davies firing a long-range effort wide in the closing minutes.
Cardiff Blues' run of Welsh derbies comes to an end next week as they head down west to take on Scarlets in Llanelli.
Following a frenetic start, in which both teams packed plenty of punch, Cardiff began to build multiple phases as the 10 minute mark passed.
With Ben Thomas pulling the strings and enjoying plenty of time on the ball, Young’s side piled on the pressure and showed real patience. Wave after wave of attack came and just when it looked to be fizzling out, Rhys Carré contributed with a colossal carry.
It left the Dragons on the back foot and when play was spread to the left, Thomas ghosted through and freed his hands to release Adams, who scorched past Ioan Davies, on a short, inside line.
The wing needed no second invitation and raced clear for his ninth try in 15 games for the region. Thomas added the extras to give his side a seven point advantage and it could have been more.
Virtually straight from the restart Olly Robinson found himself in possession on the left and he combined with Sam Moore and Cory Hill as the forwards galloped down the wing.
Again, the Blues built pressure and space was created on the right, however Thomas did not have the time to release an accurate pass with Roberts roaring forward on the spot rush.
The opportunity was lost but Cardiff settled for three points with Roberts failing to wrap as Thomas flicked the ball on.
There were further opportunities to extend the advantage with Olly Robinson and Dillon Lewis causing chaos at the breakdown but shots at goal were turned down.
As the half an hour mark passed, the Dragons built into the encounter with Roberts, Aaron Wainwright and Taine Basham all carrying hard.
It appeared as though a score was inevitable for the visitors but tight-head Lewis, who was clearly fired up for the occasion, swooped for a second crucial turnover in front of the on watching Wales coaches.
Cardiff continued to threaten in attack but it was the Newport outfit next on the scoreboard as Sam Davies opened his side’s account after Seb Davies was pinged for a late tackle.
Cardiff were dealt a major blow five minutes into the second half when Owen Lane was sent off for a shoulder to the head of Gozalo Bertranou. It was unfortunate for Lane, who attempted to pull out of contact as the Argentine scrum-has flicked a pass out the back.
Play came back for another penalty, which Wainwright tapped quickly and knocked on but Mike Adamson could not ignore the television replays and he came back again to eventually give Lane his marching orders.
The Dragons subsequently laid siege to the Cardiff try-line and increasingly benefitted from refereeing decisions. Taylor Davies eventually crashed over with Davies adding the extras and soon after a penalty to take the lead for the first time.
Buoyed by their try and numerical advantage the Dragons turned the screw and pushed for a second try. It was desperate stuff at times for Cardiff, who were now clinging on.
With a red card replacement allowed after 20 minutes, Ben Thomas was taken off for Jarrod Evans, safe in the knowledge we could come back.
But the Blues woes were further compounded as Jason Harries was perhaps harshly sin-binned for a knock on as the onslaught continued.
It appeared ominous for the home side as Jonah Holmes raced towards the corner but Adams and Amos did enough to hold him out and the tireless Turnbull secured a crucial turnover.
Davies nudged the visitors further in front with a long-range penalty on 68 minutes but they failed to do with the restart, with the ball hacked through and then booted into touch by Ross Moriarty.
Dai Young's men ensured they were clinical in taking points away from a rare second half visit to the opposition 22, as Teddy Williams crashed over for his first score in Cardiff colours.
Evans added the extras to edge his side ahead, and things went from bad to worse for Dragons as a Captain's Challenge saw Rhys Lawrence shown a red card for a high shot on Turnbull in the build up.
The visitors did have a late opportunity to regain the lead, but Davies' long range strike was pushed wide.