Apex domains cannot have CNAME records.
Question and response
Question
dig i40transmission.com. NS
Answer
i40transmission.com. 3 NS ns-1808.awsdns-34.co.uk.
i40transmission.com. 3 NS ns-729.awsdns-27.net.
i40transmission.com. 3 NS ns-1037.awsdns-01.org.
i40transmission.com. 3 NS ns-1640.awsdns-13.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0