Apex domains cannot have CNAME records.
Question and response
Question
dig itc.cdc.telia.net. NS
Answer
itc.cdc.telia.net. 5 NS f1.teliadns.fi.
itc.cdc.telia.net. 5 NS s1.teliadns.se.
itc.cdc.telia.net. 5 NS n1.teliadns.no.
itc.cdc.telia.net. 5 NS s2.teliadns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0