Apex domains cannot have CNAME records.
Question and response
Question
dig 117.54.66.in-addr.arpa. NS
Answer
117.54.66.in-addr.arpa. 3 NS ns3-core-auth-usfl001.digicelgroup.com.
117.54.66.in-addr.arpa. 3 NS ns2-core-auth-jm.digicelgroup.com.
117.54.66.in-addr.arpa. 3 NS ns3.digicelbroadband.com.
117.54.66.in-addr.arpa. 3 NS ns1.digicelbroadband.com.
117.54.66.in-addr.arpa. 3 NS ns0.digicelbroadband.com.
117.54.66.in-addr.arpa. 3 NS dns0.digiceljamaica.net.
117.54.66.in-addr.arpa. 3 NS ns2-sub-jm.digicelgroup.com.
117.54.66.in-addr.arpa. 3 NS ns4-core-auth-usny001.digicelgroup.com.
Authority
The response has no authority records.
Additional
ns0.digicelbroadband.com. 3 A 66.54.116.2
ns1.digicelbroadband.com. 3 A 66.54.116.10
ns3.digicelbroadband.com. 3 A 66.54.126.22
dns0.digiceljamaica.net. 3 A 66.54.117.224
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0