Apex domains cannot have CNAME records.
Question and response
Question
dig hringdu.is. NS
Answer
hringdu.is. 5 NS ns2.hringdu.is.
hringdu.is. 5 NS ns1.hringdu.is.
Authority
The response has no authority records.
Additional
ns1.hringdu.is. 5 A 46.22.100.2
ns2.hringdu.is. 5 A 139.162.244.194
ns1.hringdu.is. 5 AAAA 2a00:5000:0:a2:0:0:0:2
ns2.hringdu.is. 5 AAAA 2a01:7e00:0:0:f03c:94ff:fe92:4787
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0