Apex domains cannot have CNAME records.
Question and response
Question
dig fibertelecom.com. NS
Answer
fibertelecom.com. 5 NS ns.fibertelecom.com.
fibertelecom.com. 5 NS ns.fibertelecom.nl.
fibertelecom.com. 5 NS ns.fibertelecom.it.
Authority
The response has no authority records.
Additional
ns.fibertelecom.it. 5 A 93.94.94.12
ns.fibertelecom.nl. 5 A 93.94.94.13
ns.fibertelecom.com. 5 A 31.185.102.11
ns.fibertelecom.nl. 5 AAAA 2a03:b020:0:501:93:94:94:13
ns.fibertelecom.com. 5 AAAA 2a03:b020:41:327:31:185:102:11
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0