Apex domains cannot have CNAME records.
Question and response
Question
dig terra.com. NS
Answer
terra.com. 5 NS a11-66.akam.net.
terra.com. 5 NS a.dns.terra.com.
terra.com. 5 NS a1-19.akam.net.
terra.com. 5 NS a6-66.akam.net.
terra.com. 5 NS c.dns.terra.com.
terra.com. 5 NS a13-65.akam.net.
terra.com. 5 NS a24-67.akam.net.
terra.com. 5 NS a28-64.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0