Apex domains cannot have CNAME records.
Question and response
Question
dig publicis.com. NS
Answer
publicis.com. 5 NS ns5.publicisgroupe.com.
publicis.com. 5 NS ns3.publicisgroupe.com.
publicis.com. 5 NS ns1.publicisgroupe.com.
Authority
The response has no authority records.
Additional
ns1.publicisgroupe.com. 2 A 167.246.0.200
ns3.publicisgroupe.com. 2 A 81.200.177.1
ns5.publicisgroupe.com. 2 A 180.235.155.185
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0