After five games without a league win the visit of Cardiff had the feel of a key relegation battle and Schar's 24th-minute opener eased the tension around the ground.
Finding himself in an advanced position the Swiss international centre back drove in from near the touchline and with no pressure from Cardiff's defenders took aim and curled a superb shot past keeper Neil Etheridge.
It was Schar's first goal for Newcastle since joining from Spanish club Deportivo La Coruna and having got the taste for it he doubled his side's lead when bundling the ball into the net from a Matt Ritchie corner just past the hour mark.
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Schar became the first Newcastle defender to score two goals in a game since Philippe Albert in 1996.
Cardiff offered little in response apart from the odd flurry and Schar was not far away from claiming a hat-trick when he headed off target from another Ritchie corner.
Ayoze Perez added some late gloss, tapping in Newcastle's third in stoppage time from Salomon Rondon's cross.
Newcastle climbed to 17th with 21 points, one place above the drop zone while Cardiff are in 18th spot, with 19 points.
"We did good. We scored three goals so everyone has to be happy," Benitez said.
"The main thing is the commitment of the players and then it was about trying to manage the game against a tough team, a physical team."
(Reporting by Martyn Herman; Editing by Toby Davis)
