Apex domains cannot have CNAME records.
Question and response
Question
dig gdsx.com. NS
Answer
gdsx.com. 5 NS ns-808.awsdns-37.net.
gdsx.com. 5 NS ns-316.awsdns-39.com.
gdsx.com. 5 NS ns-1730.awsdns-24.co.uk.
gdsx.com. 5 NS ns-1161.awsdns-17.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0