Apex domains cannot have CNAME records.
Question and response
Question
dig 16100.fi. NS
Answer
16100.fi. 5 NS ns3.neutech.fi.
16100.fi. 5 NS ns4.neutech.fi.
Authority
The response has no authority records.
Additional
ns3.neutech.fi. 5 A 94.199.59.155
ns4.neutech.fi. 5 A 185.28.247.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0