Apex domains cannot have CNAME records.
Question and response
Question
dig ptr.cidc.telus.com. NS
Answer
ptr.cidc.telus.com. 5 NS dns1.cidc.telus.com.
ptr.cidc.telus.com. 5 NS dns2.cidc.telus.com.
Authority
The response has no authority records.
Additional
dns1.cidc.telus.com. 4 A 216.123.224.131
dns2.cidc.telus.com. 4 A 66.203.199.203
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0