Montpellier ran in five tries in a 33-8 rout of Top 14 leader Lyon as Bordeaux-Begles closed the gap at the summit by edging past Racing 92.
Lyon, which was beaten in the semi-finals last season, had won eight of its first nine games in this campaign but was blown away by Montpellier, which was 21-0 up at half-time thanks to tries from Nemani Nadolo, Bismarck Du Plessis and Louis Picamoles.
The visitors finally got on the board with a Jonathan Wisniewski penalty in the 51st minute but further scores from Nico Janse van Rensburg and Youri Delhommel increased Montpellier's lead before Xavier Mignot crossed for a consolation late on.
Bordeaux took advantage of Lyon's slip-up with a 34-30 victory over Racing as Matthieu Jalibert provided 14 points from the boot.
It was announced this week that Semi Radradra will join Premiership side Bristol Bears for next season but the Fiji international showed he was not distracted by his upcoming move with two of Bordeaux's four tries.
Sergio Parisse scored Toulon's try in a 19-9 success over Pau, while Brock James and Jules Plisson kicked five penalties between them as La Rochelle defeated Castres 22-13.
Clermont Auvergne was also victorious, a strong second-half display helping it to a 30-13 triumph over Agen.