Apex domains cannot have CNAME records.
Question and response
Question
dig ip-5-135-141.eu. NS
Answer
ip-5-135-141.eu. 1 NS ns102.ovh.net.
ip-5-135-141.eu. 1 NS dns102.ovh.net.
Authority
The response has no authority records.
Additional
ns102.ovh.net. 5 A 5.135.54.1
dns102.ovh.net. 5 A 5.196.38.181
ns102.ovh.net. 5 AAAA 2001:41d0:b00:f600:0:0:0:2
dns102.ovh.net. 5 AAAA 2001:41d0:d00:fc00:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0