Reigning champions Real Madrid beat Barcelona 3-1 in the Clasico to overtake their fierce rivals at the top of La Liga on Sunday.
Karim Benzema opened the scoring in the 12th minute by converting a rebound after Marc-Andre ter Stegen saved from Vinicius Junior, with Fede Valverde drilling home the second from the edge of the box before the break.
Ferran Torres pulled one back for Barcelona in the final stages after good work by Ansu Fati, but Rodrygo won and converted a late penalty to ensure Carlo Ancelotti's side inflicted Barcelona's first domestic defeat of the season.
Madrid ended the Catalans' seven-game winning streak in the league and added to the still-raw pain of their struggles in Europe, where they are on the verge of Champions League elimination.
Barcelona, who spent heavily in the summer to try and catch up with their rivals, now trail them by three points. The Catalans had conceded just one league goal in eight games before the Clasico but shipped double that tally in the first half, leaving Madrid as the division's only unbeaten side.
After a damaging draw with Inter Milan midweek that left Barcelona's European hopes hanging by a thread, Xavi made changes.
Jules Kounde returned after injury to strengthen the defence, with veteran defender Gerard Pique, who made a costly error against the Italians, dropping out. Frenkie de Jong and Alejandro Balde also came into the side.
Xavi's counterpart Ancelotti had fewer decisions to make, with Valverde getting the nod over Rodrygo on the right of the attack, while Andriy Lunin started in goal with Thibaut Courtois not ready to return after suffering sciatica.
Last season Barcelona's best moment came at the Bernabeu, as Xavi's side earned a surprising 4-0 win, but this visit found them at their lowest ebb since the Spanish World Cup winner took charge.
- Benzema on the money -
Vinicius probed in the opening stages down the left flank against the unconvincing Sergi Roberto and that was where Madrid's opening goal came from after 12 minutes.
The masterful Toni Kroos held off Sergio Busquets and threaded a neat pass down the wing, with Vinicius leaving Roberto for dead. Ter Stegen denied the Brazilian winger, but Benzema was on hand to slam home the rebound.
The French forward had gone five games without a goal, but ended his drought on the big stage, showing typically perfect timing as he is expected to win the Ballon d'Or in Paris on Monday.
The visitors should have levelled when Raphinha fired a cross along the six-yard box which De Jong missed and then Lewandowski, at full stretch, sent high over the crossbar.
The Polish striker, La Liga's top scorer on nine goals, could barely believe he had missed, although he might have been offside.
Vinicius was booked for complaining about a push from Roberto as Barcelona began to earn a foothold in the game, but another individual error quickly pulled it away from them.
Eric Garcia's loose header found Vinicius in a dangerous area and Madrid toyed with Barcelona's defence, dragging them one way before Ferland Mendy passed the ball back across for Valverde to drill home from the edge of the area.
Madrid continued to push forward after the break and Benzema curled home a third, but it was ruled out for offside.
At the other end Lewandowski sent a free-kick into the wall and appealed for a penalty after Dani Carvajal collided with him in the box, but the referee was not interested.
Substitute Fati angled a strike wide from outside the area but Madrid were largely comfortable, sitting back and keeping Barcelona at arm's length until Torres struck.
Fati's brilliant run and cross for the Spanish winger gave Barcelona a lifeline, but Madrid sealed the win when Garcia trod on Rodrygo in the area and he beat Ter Stegen from the spot.