While the Japan global was introduced in the second half, Rondon remained an unused substitute - much to the bewilderment of the Magpies faithful.
Kenedy stepped up to take the spot-kick but his weak effort was palmed out by Etheridge in what was the final moment of action, capping a miserable afternoon for the Brazilian.
The Bluebirds nearly lost their second consecutive game in the league when club captain Sean Morrison conceded a penalty after he handled Yoshinori Muto's cross.
He later missed a glorious opportunity to earn the Magpies their first victory of the season.
Ayoze Perez made a vital block when Cardiff defender Sol Bamba headed Joe Ralls' corner goalwards in the 10th minute.
Both sides had chances in a lively start spiced up by a rash Matt Ritchie challenge which saw the Newcastle wideman cautioned.
Benitez still plans to loan out 22-year-old right-back Jamie Sterry, who had a spell at Crewe Alexandra last season.
Craig Pawson deemed Hayden's tackle on Josh Murphy from behind as unsafe, and the referee made another huge call seconds from the end to punish Cardiff captain Sean Morrison for handball. Let's take a closer look at the scoreless draw.
Isaac Hayden: He gave Kenedy a run for his money on poor form today.
Needless to say, it's a clear red card - but Craig Pawson didn't agree!
Cardiff pressed and pressed to get a goal but they just couldn't find one.
It could have been worse, however, when a penalty was awarded against Sean Morrison deep into stoppage time.
You'll seldom see a better debut than this.
54' A good chance for Zohore there as the ball is played into the box, but he's not moved quickly enough and he's not well positioned to deal with it. Newcastle will not leave with three points, after all.