Apex domains cannot have CNAME records.
Question and response
Question
dig jump4.com. NS
Answer
jump4.com. 4 NS ns1.hover.com.
jump4.com. 4 NS ns2.hover.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0