Apex domains cannot have CNAME records.
Question and response
Question
dig dynv6.com. NS
Answer
dynv6.com. 5 NS ns1.digineo.de.
dynv6.com. 5 NS ns2.digineo.de.
dynv6.com. 5 NS ns3.digineo.de.
Authority
The response has no authority records.
Additional
ns1.digineo.de. 5 A 5.45.100.168
ns2.digineo.de. 5 A 195.201.93.228
ns3.digineo.de. 5 A 185.117.215.53
ns1.digineo.de. 5 AAAA 2a03:4000:6:568:0:0:0:1
ns2.digineo.de. 5 AAAA 2a01:4f8:1c1c:5172:0:0:0:1
ns3.digineo.de. 5 AAAA 2a06:8781:0:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0