Apex domains cannot have CNAME records.
Question and response
Question
dig pphosted.COM. NS
Answer
pphosted.com. 3 NS pdns99.ultradns.biz.
pphosted.com. 3 NS ns3.proofpoint.com.
pphosted.com. 3 NS pdns99.ultradns.net.
pphosted.com. 3 NS pdns99.ultradns.org.
pphosted.com. 3 NS ns1.proofpoint.com.
pphosted.com. 3 NS pdns99.ultradns.com.
Authority
The response has no authority records.
Additional
ns1.proofpoint.com. 3 A 208.84.67.208
ns3.proofpoint.com. 3 A 208.84.66.208
pdns99.ultradns.biz. 3 A 156.154.66.99
pdns99.ultradns.net. 3 A 156.154.65.99
pdns99.ultradns.org. 3 A 156.154.67.99
ns1.proofpoint.com. 3 AAAA 2620:100:9000:1:0:0:0:d0
ns3.proofpoint.com. 3 AAAA 2620:100:9004:1:0:0:0:d0
pdns99.ultradns.biz. 3 AAAA 2610:a1:1015:0:0:0:0:87
pdns99.ultradns.net. 3 AAAA 2610:a1:1014:0:0:0:0:87
pdns99.ultradns.org. 3 AAAA 2001:502:4612:0:0:0:0:87
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0