Apex domains cannot have CNAME records.
Question and response
Question
dig pir-ns.org. NS
Answer
pir-ns.org. 5 NS v0n2.pir-ns.org.
pir-ns.org. 5 NS v0n1.pir-ns.org.
pir-ns.org. 5 NS v2n0.pir-ns.org.
pir-ns.org. 5 NS v2n1.pir-ns.org.
pir-ns.org. 5 NS v0n0.pir-ns.org.
pir-ns.org. 5 NS v0n3.pir-ns.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0