First half goals by Ayoze Diaz and Felipe Melo got Racing the three points and left Real the two-week winter break to ponder how it is going to revitalize its season.
The defeat means Real slips to fifth and is now 11 points behind league leaders and bitter rival Barcelona, which beat Celta Vigo 2-0 on Tuesday, with Samuel Eto'o scoring both goals for the Catalan club.
Barcelona has 40 points from 17 games, five clear of second-placed Osasuna although the Pamplona-based side has a game in hand and was to play Atletico Madrid yesterday.
Although Ronaldo got one back with a header after 67 minutes, and had another close effort late in the game, Real players left the field once again with the crowd whistling in their ears.
"We know we are going through difficult times," conceded Real coach Juan Ramon Lopez Caro, who knows the pressure will inevitably increase on him after only taking over former Brazil boss Wanderley Luxemburgo two weeks ago. Lopez Caro has won only one of his four games since taking over at the Real helm and has yet to win at the Bernabeu.
He was given the backing of Real president Florentino Perez until the end of the season on Monday but the former Real reserve team coach could find that he is looking for another job sooner if he fails to get better results quickly.
A further negative note was struck when David Beckham was booked early in the game. The England captain will now miss Real's first league game of 2006, a tough away trip at Villarreal on January 8.
In other Primera Liga action: Villarreal 0, Malaga 0; Valencia 3, Real Mallorca 0; Deportivo La Coruna 1, Espanyol 2; Real Betis 3, Alaves 0.
Fabio Capello insisted his Juventus side was capable of sustaining their irresistible form which has seen them drop just five points in 17 Serie A matches.
"It's very difficult to maintain this rhythmn but we have the will and the legs to do so," he said after Wednesday's 2-0 home victory against Siena whd32ich took the reigning champion into the two-week winter break with an eight-point lead.
Fabio Cannavaro opened the scoring with a firm header before David Trezeguet's lob sealed the Turin club's 15th win.
Meanwhile, second-placed Inter thrashed Empoli 4-1 at the San Siro, but its sixth consecutive league win was marred by a head injury to Brazilian striker Adriano.
The Brazil international briefly lost consciousness after colliding with Andrea Raggi and was quickly rushed to hospital.
Inter coach Roberto Mancini said Adriano was not seriously hurt but would stay there overnight as a precaution.
AC Milan remains nine points off the pace in third place after inflicting a first home defeat on Livorno. Alberto Gilardino scored twice for Carlo Ancelotti's side before Andriy Shevchenko rounded off a comfortable 3-0 win. And Fiorentina held on to fourth place after Martin Jorgensen's goal gave it a 1-0 home win over Palermo.
Juventus have 46 points followed by Inter on 38, AC Milan on 37 and Fiorentina on 36.
In other Serie A action: Roma 4, Chievo 0; Udinese 2, Sampdoria 0; Parma 1, Cagliari 0; Ascoli 1, Treviso 0; Lecce 0, Lazio 0; Messina 1, Reggina 1.