Apex domains cannot have CNAME records.
Question and response
Question
dig smartape-vps.com. NS
Answer
smartape-vps.com. 5 NS ns2.smartape.net.
smartape-vps.com. 5 NS ns1.smartape.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0