Apex domains cannot have CNAME records.
Question and response
Question
dig 192-223.181.104.184.in-addr.arpa. NS
Answer
192-223.181.104.184.in-addr.arpa. 5 NS ns2.webworld.org.
192-223.181.104.184.in-addr.arpa. 5 NS ns1.webworld.org.
192-223.181.104.184.in-addr.arpa. 5 NS ns3.webworld.org.
Authority
The response has no authority records.
Additional
ns1.webworld.org. 5 A 217.115.112.2
ns2.webworld.org. 5 A 217.115.115.2
ns3.webworld.org. 5 A 95.217.54.131
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0