Apex domains cannot have CNAME records.
Question and response
Question
dig roso.dk. NS
Answer
roso.dk. 2 NS chelsea.ns.cloudflare.com.
roso.dk. 2 NS keaton.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0