Madrid are now within two points of champions Barcelona, who wrapped up Club World Cup glory in Japan earlier on Sunday, but the bizarre nature of this rout is unlikely to bring many Benitez doubters onside.
Rayo tore forward from kick-off, only to leave themselves exposed to a slick third-minute counter-attack.
James Rodriguez and Bale combined, and the Welshman released overlapping full-back Danilo to steer a low effort past visiting keeper Yoel.
But Paco Jemez’s team would not be discouraged and they deservedly drew level when Amaya headed Roberto Trashorras’ corner past a flimsy attempted save from Keylor Navas in the 10th minute.
Worse was to come two minutes later for Madrid – Jozabed planting Tito’s deflected cross into the corner to stun the Bernabeu – and the attacking midfielder almost made it three when Navas beat a shot behind at the near post with his defence in disarray.
A breathless match took its latest remarkable turn in the 14th minute when Tito was rightly dismissed for a reckless lunge on Kroos, who recovered to fire a blistering drive narrowly wide.
Much had happened in the 24 minutes since Danilo opened the scoring but the Brazilian hooked in a wonderful cross for Bale to bury a headed equaliser.
The carnage was far from over and Rayo were down to nine men in the 28th minute as referee Ignacio Iglesias Villanueva gave Baena a second yellow card for tangling with Sergio Ramos inside the area.
Paco’s team were understandably aggrieved as Ronaldo coolly drilled home the resulting penalty.
James sent Bale streaking through the undermanned Rayo ranks to double his tally and the same combination almost heralded a first-half hat-trick in stoppage time, but the ex-Tottenham man could not convert at the far post.
The utterly surreal feel to proceedings was heightened when Real were whistled at half-time and they sought to repair these fractured relations with their fans as Benzema slotted home number five, James the provider once more.
Yoel was out sharply to deny Ronaldo in the 50th minute but his was a thankless task and there was nothing he could do when the Portuguese superstar firmly nodded James’ left-wing cross into the net.
Rayo attacked when possible, left-back Nacho having a venomous shot blocked, heralding the unlikely sight of nine men conceding their seventh on the break after 61 minutes.
James released Ronaldo to leave Bale with a simple finish for the matchball and he had a fourth when an attempted nutmeg on substitute Quini fell favourably.
Luka Modric found an unmarked Benzema to dispatch number nine and there would be a second hat-trick when he thumped in a lay-off from substitute Mateo Kovacic left footed – concluding a scarcely credible contest in the Spanish capital.