Apex domains cannot have CNAME records.
Question and response
Question
dig smhost.pro. NS
Answer
smhost.pro. 1 NS ns2.smhost.pro.
smhost.pro. 1 NS ns1.smhost.pro.
Authority
The response has no authority records.
Additional
ns1.smhost.pro. 1 A 212.75.96.49
ns2.smhost.pro. 1 A 212.75.96.19
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0