Apex domains cannot have CNAME records.
Question and response
Question
dig slidesdobem.com. NS
Answer
slidesdobem.com. 4 NS ns-53.awsdns-06.com.
slidesdobem.com. 4 NS ns-716.awsdns-25.net.
slidesdobem.com. 4 NS ns-722.awsdns-26.net.
slidesdobem.com. 4 NS ns-756.awsdns-30.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0