Bayonne won the Rugby Pro D2 title last season to seal its return to the top flight and used that momentum to spring a surprise as it visited Racing in the first round of fixtures.
The visitors trailed 17-7 at half-time after Michael Ruru's try only briefly cancelled out a Racing lead that was forged by Yoan Tanga Mangene and restored by Juan Imhoff.
But after Teddy Iribaren's penalty on the stroke of half-time, Racing did not score again.
Romain Barthelemy kicked four second-half penalties of his own, while Aymeric Luc added a second Bayonne try, as Racing's ill discipline cost it, with Tanga Mangene and Hassane Kolingar each shown yellow cards.
Fellow promoted side Brive had a less successful return to the big time as it lost 33-14 at Pau, despite seeing the hosts reduced to 14 men after just 20 minutes.
Pau led 7-0 at the time of Matthieu Ugena's dismissal and managed to stretch its advantage to 23-14 before Brive's Joris Jurand saw red, with the home side then running in two late tries.
Elsewhere, champion Toulouse was beaten in the first match of its title defence, going down 30-25 at Bordeaux-Begles.
The sides shared five tries, eight penalties and three yellow cards, with Matthieu Jalibert decisively crossing moments after Selevasio Tolofua's 65th-minute sin-binning.
Lyon thrashed Stade Francais 43-9 for a bonus point, which Toulon also claimed as it triumphed 44-25 at Agen.
Castres and Montpellier were separated by just two points either side of the play-off line last season and the former, a loser on that occasion, edged victory by a point on Sunday (AEST).