Apex domains cannot have CNAME records.
Question and response
Question
dig pro. NS
Answer
pro. 5 NS c0.pro.afilias-nst.info.
pro. 5 NS b0.pro.afilias-nst.org.
pro. 5 NS a0.pro.afilias-nst.info.
pro. 5 NS a2.pro.afilias-nst.info.
pro. 5 NS b2.pro.afilias-nst.org.
pro. 5 NS d0.pro.afilias-nst.org.
Authority
The response has no authority records.
Additional
a0.pro.afilias-nst.info. 5 A 199.182.0.1
a2.pro.afilias-nst.info. 5 A 199.182.32.1
b0.pro.afilias-nst.org. 5 A 199.182.1.1
b2.pro.afilias-nst.org. 5 A 199.182.40.1
c0.pro.afilias-nst.info. 5 A 199.182.16.1
d0.pro.afilias-nst.org. 5 A 199.182.17.1
a0.pro.afilias-nst.info. 5 AAAA 2001:500:c0:0:0:0:0:1
a2.pro.afilias-nst.info. 5 AAAA 2001:500:e0:0:0:0:0:1
b0.pro.afilias-nst.org. 5 AAAA 2001:500:c1:0:0:0:0:1
b2.pro.afilias-nst.org. 5 AAAA 2001:500:e1:0:0:0:0:1
c0.pro.afilias-nst.info. 5 AAAA 2001:500:d0:0:0:0:0:1
d0.pro.afilias-nst.org. 5 AAAA 2001:500:d1:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0