Apex domains cannot have CNAME records.
Question and response
Question
dig ipv6.uvsq.fr. NS
Answer
ipv6.uvsq.fr. 5 NS soleil.uvsq.fr.
ipv6.uvsq.fr. 5 NS lune.uvsq.fr.
ipv6.uvsq.fr. 5 NS shiva.jussieu.fr.
ipv6.uvsq.fr. 5 NS resone.univ-rennes1.fr.
Authority
The response has no authority records.
Additional
lune.uvsq.fr. 5 A 193.51.33.28
shiva.jussieu.fr. 5 A 134.157.0.129
resone.univ-rennes1.fr. 5 A 129.20.254.1
soleil.uvsq.fr. 5 A 193.51.24.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0