Apex domains cannot have CNAME records.
Question and response
Question
dig iwelt.domains. NS
Answer
iwelt.domains. 5 NS anycast2.iwelt.domains.
iwelt.domains. 5 NS anycast.iwelt.de.
Authority
The response has no authority records.
Additional
anycast2.iwelt.domains. 5 A 176.97.158.102
anycast2.iwelt.domains. 5 AAAA 2001:67c:10b8:0:0:0:0:102
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0