Apex domains cannot have CNAME records.
Question and response
Question
dig bluebyte.dk. NS
Answer
bluebyte.dk. 5 NS amir.ns.cloudflare.com.
bluebyte.dk. 5 NS bingo.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0