Apex domains cannot have CNAME records.
Question and response
Question
dig 19.in-addr.arpa. NS
Answer
19.in-addr.arpa. 5 NS dns006.ford.com.
19.in-addr.arpa. 5 NS extdns001.ford.com.
19.in-addr.arpa. 5 NS extdns002.ford.com.
19.in-addr.arpa. 5 NS dns005.ford.com.
Authority
The response has no authority records.
Additional
dns005.ford.com. 5 A 19.12.18.20
dns006.ford.com. 5 A 19.12.34.81
extdns001.ford.com. 5 A 19.12.77.20
extdns002.ford.com. 5 A 19.12.93.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0