Before using this command it is important to understand what a self-signed certificate implies. Also, a self-signed certificate will always be classified as not secure by senhasegura.
Create RSA Key:
openssl genrsa -out [key_name].key 4096[key_size]
Create subscription .csr:
openssl req -key [created_key_name].key -new -out [signature_name].csr
Generate a self-signed certificate:
openssl x509 -signkey [key_name].key -in [signature_name].csr -req -days 365[certificate validity] -out [certificate].crt