Apex domains cannot have CNAME records.
Question and response
Question
dig tdccloud.dk. NS
Answer
tdccloud.dk. 5 NS authns003.yacn.dk.
tdccloud.dk. 5 NS authns002.yacn.dk.
tdccloud.dk. 5 NS authns001.yacn.dk.
Authority
The response has no authority records.
Additional
authns001.yacn.dk. 5 A 213.174.84.205
authns002.yacn.dk. 5 A 2.106.41.246
authns003.yacn.dk. 5 A 137.117.161.172
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0