Apex domains cannot have CNAME records.
Question and response
Question
dig reverse.alphalink.fr. NS
Answer
reverse.alphalink.fr. 5 NS ns1.alphalink.fr.
reverse.alphalink.fr. 5 NS ns2.alphalink.fr.
Authority
The response has no authority records.
Additional
ns1.alphalink.fr. 5 A 217.15.80.4
ns2.alphalink.fr. 5 A 217.15.88.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0