Apex domains cannot have CNAME records.
Question and response
Question
dig vtx1.org. NS
Answer
vtx1.org. 5 NS nsc.vtx1.net.
vtx1.org. 5 NS nsb.vtx1.net.
vtx1.org. 5 NS nsf.vtx1.net.
vtx1.org. 5 NS nsa.vtx1.net.
vtx1.org. 5 NS nse.vtx1.net.
vtx1.org. 5 NS nsd.vtx1.net.
vtx1.org. 5 NS nsg.vtx1.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0