Followed another tutorial and adapted the certificate creation to:
openssl req -new -x509 -days 365 -utf8 -out cert.pem -keyout key.pem
I opted to populate the default config file with the answers to the questions (instead of supplying them via the prompt) and added a commented non-ASCII character just to make sure it's a unicode file (kinda unnecessary i guess but file
made me happy by saying UTF-8 Unicode text).