Salford (6) 12 Tries: Gibson, Henry Goals: Holdsworth 2
Westerman has now kicked 27 Super League goals this season for Cas
Castleford ended a run of four straight defeats as they battled back from last weekend's Challenge Cup exit to Barrow.
After Ryan McGoldrick's opener and the first three of Joe Westerman's seven kicks earned a 10-6 half-time lead, the Tigers ran in three second-half tries.
Mitchell Sargent, Jordan Thompson and Stuart Jones all crossed.
And, although Ashley Gibson and Mark Henry replied with tries for Salford, the visitors remain stuck in 12th place after a fifth away league defeat.
Cas had won only once in front of their own fans at The Jungle in six attempts this season, including last weekend's 34-28 cup exit to Championship side Barrow.
But, in a scrappy game, Westerman proved their key man as he found his touch with the boot.
The Tigers welcomed back Australian scrum-half Brent Sherwin for his 50th appearance and prop Liam Higgins, who both missed the defeat against Barrow because of shoulder injuries.
Salford recalled winger Steve Tyrer in place of Jodie Broughton, sidelined after aggravating a shoulder injury.
But, with half-backs Rangi Chase and Sherwin dictating play, it was no surprise when they set up centre McGoldrick to earn Cas a sixth-minute lead.
Two goals in three minutes from loose forward Westerman stretched Cas clear at 10-0 but, on the stroke of half-time, Salford grabbed a lifeline.
Chase lost the ball near his own posts and Daniel Holdsworth's clever chip-kick set up a try for Ashley Gibson.
Holdsworth converted to reduce the half-time deficit to four points. But Castleford increased their lead 13 minutes after the break when Ryan Hudson's deft pass sent Aussie prop Sargent plunging over.
Salford struck back nine minutes later when Gibson's crossfield kick led to Henry scoring, Holdsworth adding the extras to cut the gap to 16-12.
But, just when the Tigers looked to be wobbling, they were given a huge lift when young full-back Thompson scored from Chase's well-placed kick.
Westerman converted that, before adding another penalty. And the cake was iced two minutes from time when Sherwin's kick set up a try for Jones, allowing Westerman to add his seventh goal.
Castleford coach Terry Matterson:
"We got the result and that was important. There were things we can do better but we controlled possession, we controlled field position and we controlled the scoreboard.
"We got a little bit nervous and that's understandable considering what we've come through and what happened last week against Barrow but we played for the 80 minutes and we rattled up 30 points which is quite pleasing.
"Joe Westerman landed seven goals from seven kicks. He hit the ball well and that makes a big difference when he is edging you two points forward especially in those wet conditions."
Salford City Reds coach Shaun McRae:
"We turned over too much football and put ourselves under enormous pressure defensively.
"We didn't have enough field position or possession. The stats say Castleford had 51 sets in the game and we had 39.
"Castleford's completion rate in the second half was an unbelievable 96% and we just couldn't get the ball off them.
"We pushed balls today when we shouldn't have and we were a bit loose in the carry. That's the frustrating part of our game, We probably built more pressure on ourselves than the opposition did."
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