Apex domains cannot have CNAME records.
Question and response
Question
dig ttnlearning.com. NS
Answer
ttnlearning.com. 4 NS ns-248.awsdns-31.com.
ttnlearning.com. 4 NS ns-887.awsdns-46.net.
ttnlearning.com. 4 NS ns-1126.awsdns-12.org.
ttnlearning.com. 4 NS ns-2005.awsdns-58.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0