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