Apex domains cannot have CNAME records.
Question and response
Question
dig cuuma.fi. NS
Answer
cuuma.fi. 5 NS ns4.cuuma.fi.
cuuma.fi. 5 NS ns5.cuuma.fi.
cuuma.fi. 5 NS ns6.cuuma.com.
Authority
The response has no authority records.
Additional
ns4.cuuma.fi. 5 A 45.135.146.36
ns5.cuuma.fi. 5 A 45.135.144.36
ns6.cuuma.com. 5 A 85.9.204.56
ns6.cuuma.com. 5 AAAA 2a04:3542:1000:910:8c7a:7ff:fea8:94d
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0