Apex domains cannot have CNAME records.
Question and response
Question
dig shopco.com. NS
Answer
shopco.com. 4 NS a.ns.shopco.com.
shopco.com. 4 NS b.ns.shopco.com.
shopco.com. 4 NS c.ns.shopco.com.
Authority
The response has no authority records.
Additional
a.ns.shopco.com. 4 A 64.98.148.146
b.ns.shopco.com. 4 A 216.40.47.210
c.ns.shopco.com. 4 A 64.98.148.147
a.ns.shopco.com. 4 AAAA 2604:4000:2800:2000:64:98:148:146
b.ns.shopco.com. 4 AAAA 2604:4000:0:d:216:40:47:210
c.ns.shopco.com. 4 AAAA 2604:4000:2800:2000:64:98:148:147
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0