Apex domains cannot have CNAME records.
Question and response
Question
dig mailxtr.com. NS
Answer
mailxtr.com. 5 NS ns1.dnssunucu.com.
mailxtr.com. 5 NS ns2.dnssunucu.com.
Authority
The response has no authority records.
Additional
ns1.dnssunucu.com. 5 A 188.119.51.254
ns2.dnssunucu.com. 5 A 77.92.137.245
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0