Apex domains cannot have CNAME records.
Question and response
Question
dig ingenta.com. NS
Answer
ingenta.com. 5 NS ns5.ingenta.com.
ingenta.com. 5 NS ns3.ingenta.com.
ingenta.com. 5 NS ns1.ingenta.com.
ingenta.com. 5 NS ns2.ingenta.com.
ingenta.com. 5 NS ns4.ingenta.com.
Authority
The response has no authority records.
Additional
ns1.ingenta.com. 5 A 5.10.31.157
ns2.ingenta.com. 5 A 5.10.31.146
ns3.ingenta.com. 5 A 209.18.110.29
ns4.ingenta.com. 5 A 5.10.31.194
ns5.ingenta.com. 5 A 5.10.31.195
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0