Apex domains cannot have CNAME records.
Question and response
Question
dig eurofiber.cloud. NS
Answer
eurofiber.cloud. 5 NS ate-ns01.ate.info.
eurofiber.cloud. 5 NS ate-ns04.ate.info.
eurofiber.cloud. 5 NS ate-ns03.ate.info.
eurofiber.cloud. 5 NS ate-ns02.ate.info.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0