Apex domains cannot have CNAME records.
Question and response
Question
dig 0-63.123.247.200.in-addr.arpa. NS
Answer
0-63.123.247.200.in-addr.arpa. 5 NS ns-406.awsdns-50.com.
0-63.123.247.200.in-addr.arpa. 5 NS ns.embratel.net.br.
0-63.123.247.200.in-addr.arpa. 5 NS ns003.nexxera.com.br.
0-63.123.247.200.in-addr.arpa. 5 NS ns-1855.awsdns-39.co.uk.
Authority
The response has no authority records.
Additional
ns.embratel.net.br. 4 A 200.255.253.241
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0