Apex domains cannot have CNAME records.
Question and response
Question
dig eurofiber.com. NS
Answer
eurofiber.com. 5 NS anycast1.dnsres.net.
eurofiber.com. 5 NS ns.nscluster.us.
eurofiber.com. 5 NS dns2.cloudns.net.
eurofiber.com. 5 NS dns1.cloudns.net.
eurofiber.com. 5 NS anycast2.dnsres.net.
Authority
The response has no authority records.
Additional
ns.nscluster.us. 5 A 198.251.86.156
dns2.cloudns.net. 5 A 185.136.97.77
ns.nscluster.us. 5 AAAA 2605:6400:10:5c1:84ee:85fb:b2b:8b37
dns2.cloudns.net. 5 AAAA 2a06:fb00:1:0:0:0:2:77
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0