spf.shopback.com.br has no NS records.
NS records for this zone are defined at shopback.com.br.
NS records for this zone are defined at shopback.com.br.
Question and response
Question
dig spf.shopback.com.br. NS
Answer
The response has no answer records.
Authority
shopback.com.br. 1800 SOA harleigh.ns.cloudflare.com. dns.cloudflare.com. 2395416027 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0