Apex domains cannot have CNAME records.
Question and response
Question
dig domainkeskus.com. NS
Answer
domainkeskus.com. 5 NS dnssec2.euronic.fi.
domainkeskus.com. 5 NS dnssec1.euronic.fi.
domainkeskus.com. 5 NS dnssec3.euronic.fi.
Authority
The response has no authority records.
Additional
dnssec1.euronic.fi. 3 A 185.55.84.26
dnssec2.euronic.fi. 3 A 31.187.85.62
dnssec3.euronic.fi. 3 A 80.83.0.52
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0