Apex domains cannot have CNAME records.
Question and response
Question
dig 255.93.77.ip.retelit.net. NS
Answer
255.93.77.ip.retelit.net. 5 NS ns2.retelit.net.
255.93.77.ip.retelit.net. 5 NS ns1.retelit.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0