Apex domains cannot have CNAME records.
Question and response
Question
dig 128-26.74.67.195.in-addr.arpa. NS
Answer
128-26.74.67.195.in-addr.arpa. 5 NS dns2.tankbar.com.
128-26.74.67.195.in-addr.arpa. 5 NS dns1.tankbar.com.
128-26.74.67.195.in-addr.arpa. 5 NS dns.tankbar.com.
Authority
The response has no authority records.
Additional
dns1.tankbar.com. 5 A 195.67.74.178
dns2.tankbar.com. 5 A 51.12.242.14
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0