Apex domains cannot have CNAME records.
Question and response
Question
dig tophosting.com. NS
Answer
tophosting.com. 2 NS ns2.tophosting.com.
tophosting.com. 2 NS ns.tophosting.com.
Authority
The response has no authority records.
Additional
ns.tophosting.com. 2 A 63.223.114.3
ns2.tophosting.com. 2 A 107.155.198.79
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0