Apex domains cannot have CNAME records.
Question and response
Question
dig 236.46.89.in-addr.arpa. NS
Answer
236.46.89.in-addr.arpa. 5 NS ns2.edis.global.
236.46.89.in-addr.arpa. 5 NS ns1.edis.global.
Authority
The response has no authority records.
Additional
ns1.edis.global. 5 A 192.174.68.12
ns2.edis.global. 5 A 176.97.158.12
ns1.edis.global. 5 AAAA 2001:67c:1bc:0:0:0:0:12
ns2.edis.global. 5 AAAA 2001:67c:10b8:0:0:0:0:12
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0