Apex domains cannot have CNAME records.
Question and response
Question
dig online-send.com. NS
Answer
online-send.com. 5 NS ns-1666.awsdns-16.co.uk.
online-send.com. 5 NS ns-75.awsdns-09.com.
online-send.com. 5 NS ns-671.awsdns-19.net.
online-send.com. 5 NS ns-1507.awsdns-60.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0