Apex domains cannot have CNAME records.
Question and response
Question
dig shellit.fi. NS
Answer
shellit.fi. 5 NS ns2.z.fi.
shellit.fi. 5 NS ns1.z.fi.
shellit.fi. 5 NS ns3.shellit.org.
shellit.fi. 5 NS ns1.shellit.org.
shellit.fi. 5 NS ns2.shellit.org.
Authority
The response has no authority records.
Additional
ns1.shellit.org. 5 A 164.215.39.224
ns2.shellit.org. 5 A 164.215.39.225
ns3.shellit.org. 5 A 5.75.253.66
ns1.shellit.org. 5 AAAA 2a03:e581:4:0:0:0:0:51
ns2.shellit.org. 5 AAAA 2a03:e581:4:0:0:0:0:52
ns3.shellit.org. 5 AAAA 2a01:4f8:c010:b53e:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0