Apex domains cannot have CNAME records.
Question and response
Question
dig infra.opensuse.org. NS
Answer
infra.opensuse.org. 5 NS ns2.opensuse.org.
infra.opensuse.org. 5 NS ns1.opensuse.org.
infra.opensuse.org. 5 NS ns4.opensuse.org.
infra.opensuse.org. 5 NS ns3.opensuse.org.
Authority
The response has no authority records.
Additional
ns1.opensuse.org. 5 A 62.146.92.204
ns2.opensuse.org. 5 A 195.135.223.53
ns3.opensuse.org. 5 A 195.135.220.54
ns4.opensuse.org. 5 A 195.135.223.54
ns1.opensuse.org. 5 AAAA 2a01:138:a004:0:0:0:0:204
ns2.opensuse.org. 5 AAAA 2a07:de40:b27e:1204:0:0:0:21
ns3.opensuse.org. 5 AAAA 2a07:de40:617e:1904:0:0:0:7
ns4.opensuse.org. 5 AAAA 2a07:de40:b27e:1204:0:0:0:22
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0