Apex domains cannot have CNAME records.
Question and response
Question
dig slipofthelip.com. NS
Answer
slipofthelip.com. 5 NS ns-644.awsdns-16.net.
slipofthelip.com. 5 NS ns-625.awsdns-14.net.
slipofthelip.com. 5 NS ns-1555.awsdns-02.co.uk.
slipofthelip.com. 5 NS ns-991.awsdns-59.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0