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