OT, self-signed ssl certificate generation

[no ssl list, posting here because it might be a platform issue]

In trying to get ssl working for apache24 I tried to follow the
instructions for self-signed certificate generation at
https://docs.freebsd.org/en/books/handbook/security/index.html
in section 16.8.1, Generating Certificates.

The first example for generating a key and signing request
behaved as expected, generating a cert.key and req.pem file.

The second example, for a self-signed certificate, adjusted to:
openssl req -new -x509 -days 365 -sha3-512 -keyout host.key -out host.crt
to  place the output files in the working directory, generated only an 
empty host.key and no host.crt

It also didn't prompt for user input, which the first example
did ask for.  

Any hints as to what I'm doing wrong would be much appreciated!

Thanks for reading,