_spf.quad9.net has no NS records.
NS records for this zone are defined at quad9.net.
NS records for this zone are defined at quad9.net.
Question and response
Question
dig _spf.quad9.net. NS
Answer
The response has no answer records.
Authority
quad9.net. 600 SOA admin1.sjc.rrdns.pch.net. hostmaster.pch.net. 1681671891 10800 3600 172800 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0