Apex domains cannot have CNAME records.
Question and response
Question
dig py. NS
Answer
py. 5 NS l.dns.py.
py. 5 NS p.dns.py.
py. 5 NS b.dns.py.
py. 5 NS c.dns.py.
py. 5 NS u.dns.py.
Authority
The response has no authority records.
Additional
b.dns.py. 46530 A 200.160.0.5
c.dns.py. 161912 A 130.59.31.30
l.dns.py. 46530 A 200.0.68.10
p.dns.py. 172527 A 204.61.216.107
u.dns.py. 46530 A 198.6.1.65
b.dns.py. 46530 AAAA 2001:12ff:0:a20:0:0:0:5
c.dns.py. 161912 AAAA 2001:620:0:ff:0:0:0:30
l.dns.py. 46530 AAAA 2801:14:a000:0:0:0:0:10
p.dns.py. 172527 AAAA 2001:500:14:6107:ad:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0