Apex domains cannot have CNAME records.
Question and response
Question
dig rz-ip.net. NS
Answer
rz-ip.net. 5 NS pns2.rz-ip.net.
rz-ip.net. 5 NS pns.rz-ip.net.
Authority
The response has no authority records.
Additional
pns.rz-ip.net. 5 A 81.169.163.43
pns2.rz-ip.net. 5 A 85.214.7.25
pns.rz-ip.net. 5 AAAA 2a01:238:10b:2300:2:1:51a9:a32b
pns2.rz-ip.net. 5 AAAA 2a01:238:10b:2301:1:0:55d6:719
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0