Apex domains cannot have CNAME records.
Question and response
Question
dig petrafield.com. NS
Answer
petrafield.com. 5 NS ns2.petrafield.com.
petrafield.com. 5 NS ns1.petrafield.com.
Authority
The response has no authority records.
Additional
ns1.petrafield.com. 5 A 57.129.147.42
ns2.petrafield.com. 5 A 51.75.166.180
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0