Apex domains cannot have CNAME records.
Question and response
Question
dig 116.in-addr.arpa. NS
Answer
116.in-addr.arpa. 4 NS ns1.apnic.net.
116.in-addr.arpa. 4 NS apnic.authdns.ripe.net.
116.in-addr.arpa. 4 NS rirns.arin.net.
116.in-addr.arpa. 4 NS ns2.apnic.net.
116.in-addr.arpa. 4 NS ns3.lacnic.net.
Authority
The response has no authority records.
Additional
ns1.apnic.net. 3 A 203.119.42.53
ns2.apnic.net. 3 A 203.119.95.53
ns1.apnic.net. 3 AAAA 2001:dd8:e:0:0:0:0:53
ns2.apnic.net. 3 AAAA 2001:ddd:0:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0