Apex domains cannot have CNAME records.
Question and response
Question
dig sub-63-45-103.myvzw.com. NS
Answer
sub-63-45-103.myvzw.com. 5 NS ns1.vzwdomain.com.
sub-63-45-103.myvzw.com. 5 NS ns2.vzwdomain.com.
Authority
The response has no authority records.
Additional
ns1.vzwdomain.com. 5 A 66.174.0.3
ns2.vzwdomain.com. 5 A 66.174.70.102
ns1.vzwdomain.com. 5 AAAA 2001:4888:8000:10:0:103:0:3
ns2.vzwdomain.com. 5 AAAA 2001:4888:8000:10:0:103:0:105
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0