Paris - France wing Noa Nakaitaci grabbed a hat-trick of tries as Clermont throttled defending Top 14 champions Racing 92 in Saturday's bonus-point 47-10 home victory.
Fiji-born Nakaitaci carved apart a Racing side without rested New Zealand great Dan Carter, with fly-half Camille Lopez and prop Davit Zirakashvili also touching down in addition to a penalty try.
Morgan Parra chipped in with 14 points in the kicking game, while Lopez nailed a drop goal as Clermont romped to a commanding win in their first game at the Stade Marcel Michelin this season.
South African fullback Sean Robinson dotted down late on for Racing, the conversion added by Albert VuliVuli, to go along with a first-half penalty from Maxime Machenaud.
"We wanted to take hold of them by the throat right from the start," said Clermont second row Arthur Iturria. "It's important against big teams like that."
Racing coach Laurent Labit admitted his side had taken a hiding, adding: "We knew it would be difficult and complicated. We were given a lesson in rugby tonight."
La Rochelle climbed to the summit as Fiji back Kini Murimurivalu scored a pair of tries in a thumping 43-18 win over promoted Lyon to keep the coastal club unbeaten and two points clear of Clermont.
Montpellier scrum-half Benoit Paillague scored one of his team's five tries while adding a further 14 points with the boot as Jake White's side cruised to a 41-13 defeat of Pau.
Australian veteran Adam Ashley-Cooper made a try-scoring return in Bordeaux-Begles' 40-20 victory at home to Bayonne, with the versatile back making his first appearance of the season having been away on Rugby Championship duty.
Stade Francais dug in for a 29-25 win over Castres despite being reduced to 14 men after Jules Plisson was sent off on 58 minutes.
The win left Stade third in the table and manager Gonzalo Quesada said his side had deserved the result.
"There is no miracle, just a team who have worked very hard since the beginning of the season," said Quesada.
"We're building a group with good spirit and resources. We were up against a Castres side who came to fight at all costs."
Lacking the dramatic edge from their 30-30 draw at Clermont, Stade Francais nevertheless gave a good show against a direct rival for the final phase and ahead of two tricky trips south to Pau and Toulouse.
The hosts again proved their efficiency up front with Plisson touching down after 15 minutes. But then as Plisson let six points go begging, Argentine flyhalf Benjamn Urdapilleta kept Castres in touch 13-9 at half-time.
Tensions escalated after the break, and although the Parisians controlled the game 19-9, a series of bad decisions, with Hugo Bonneval seeing yellow for a high tackle, and Plisson red for a charge on the back of a Castres player on the ground, the visitors pulled ahead.
Samoan wing David Smith put Castres in front 22-19 with a try on 65 minutes.
But it was short lived as three minutes later, Geoffrey Doumayrou made a dive for the line for the hosts' second try in an electric atmosphere with the Parisians reclaiming a 26-22 lead they would never relinquish.
On Sunday, under-fire Toulon will undergo a true test of their mettle when they play Toulouse, while Brive, the leaders coming into the weekend, head to Grenoble.