Apex domains cannot have CNAME records.
Question and response
Question
dig cloud.vadesecure.com. NS
Answer
cloud.vadesecure.com. 5 NS ns-1699.awsdns-20.co.uk.
cloud.vadesecure.com. 5 NS ns-831.awsdns-39.net.
cloud.vadesecure.com. 5 NS ns-455.awsdns-56.com.
cloud.vadesecure.com. 5 NS ns-1476.awsdns-56.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0