Apex domains cannot have CNAME records.
Question and response
Question
dig infogral.is. NS
Answer
infogral.is. 5 NS node-1.infogral.is.
infogral.is. 5 NS node-2.infogral.is.
infogral.is. 5 NS node-3.infogral.is.
infogral.is. 5 NS node-4.infogral.is.
Authority
The response has no authority records.
Additional
node-1.infogral.is. 5 A 78.47.56.71
node-2.infogral.is. 5 A 78.47.168.188
node-3.infogral.is. 5 A 116.203.96.227
node-4.infogral.is. 5 A 116.203.244.102
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0