Apex domains cannot have CNAME records.
Question and response
Question
dig freepraxisprep.com. NS
Answer
freepraxisprep.com. 4 NS ns1.freepraxisprep.com.
freepraxisprep.com. 4 NS ns2.freepraxisprep.com.
Authority
The response has no authority records.
Additional
ns1.freepraxisprep.com. 4 A 5.135.118.101
ns2.freepraxisprep.com. 4 A 5.39.96.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0