Apex domains cannot have CNAME records.
Question and response
Question
dig ip-51-75-11.eu. NS
Answer
ip-51-75-11.eu. 4 NS ns10.ovh.net.
ip-51-75-11.eu. 4 NS dns10.ovh.net.
Authority
The response has no authority records.
Additional
ns10.ovh.net. 3 A 5.39.20.253
dns10.ovh.net. 3 A 5.135.85.109
ns10.ovh.net. 3 AAAA 2001:41d0:b00:3a00:0:0:0:2
dns10.ovh.net. 3 AAAA 2001:41d0:d00:6100:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0