Run the command and fill the required input values.
It will generate 2 files: ca.key and ca.csr. Let the challenge password empty.

openssl req -new -newkey rsa:2048 -nodes -keyout ca.key -out ca.csr

Output:

Generating RSA private key, 2048 bit long modulus (2 primes)
..............................+++++
............+++++
e is 65537 (0x010001)
Enter pass phrase for ca1.key:
Verifying - Enter pass phrase for ca1.key:

C:\Users\odefta\Desktop\CERT>openssl req -new -newkey rsa:2048 -nodes -keyout ca.key -out ca.csr
Generating a RSA private key
...............................+++++
.................................................................+++++
writing new private key to 'ca.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:RO
State or Province Name (full name) [Some-State]:Romania
Locality Name (eg, city) []:Bucharest
Organization Name (eg, company) [Internet Widgits Pty Ltd]:AX
Organizational Unit Name (eg, section) []:AX Software
Common Name (e.g. server FQDN or YOUR name) []:AX Root CA
Email Address []:admin@ax.com

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Edit the following configuration lines (if needed.)

root-ca.conf

[ req ]
default_bits = 2048
default_keyfile = ca.key
distinguished_name = req_distinguished_name
x509_extensions = v3_ca
string_mask = nombstr
req_extensions = v3_req
[ req_distinguished_name ]
countryName = RO
countryName_default = RO
countryName_min = 2
countryName_max = 2
stateOrProvinceName = Romania
stateOrProvinceName_default = Romania
localityName = Bucharest
localityName_default = Bucharest
0.organizationName = AX
0.organizationName_default = AX
organizationalUnitName = AX Software
organizationalUnitName_default = AX Software
commonName = AX Root CA
commonName_max = 64
emailAddress = admin@ax.com
emailAddress_max = 40
[ v3_ca ]
basicConstraints = critical,CA:true
subjectKeyIdentifier = hash
[ v3_req ]
nsCertType = objsign,email,server