After the section "Self-sign and create the certificate: " from my link, you should have a CA san_domain_com.key file and a signed cert named san_domain_com.crt.
Do mind though I see an error/space missing in below command from that link:
openssl x509 -req -days 3650 -in san_domain_com.csr -signkey san_domain_com.key
-out san_domain_com.crt-extensions v3_req -extfile openssl.cnf
It should be:
openssl x509 -req -days 3650 -in san_domain_com.csr -signkey san_domain_com.key
-out san_domain_com.crt -extensions v3_req -extfile openssl.cnf
Once you have the .crt and .key files, you can do below to create the .pem file needed for lighttpd: