How to get ECSDA with p-256 and SHA256 in openSSL?

Apple requests to its APNS must use JWT (JSON Web Token) signed using a Elliptic Curve Digital Signature Algorithm aka ECSDA using a p-256 curve and a SHA256 hash. How can you sign with such params in openssl?

openssl ecparam -list_curves

shows:

secp256k1 : SECG curve over a 256 bit prime field

prime256v1: X9.62/SECG curve over a 256 bit prime field

The p-256 curve you want to use is prime256v1.

Try this:

Create private key:
openssl ecparam -genkey -name prime256v1 -noout -out private.pem

Create public key:
openssl ec -in private.pem -pubout -out public.pem

Sign something
openssl dgst -sha256 -sign private.pem yourinputdocument -out yourinput.sha256 yourinput 

To verify:
openssl dgst -sha256 -verify public.pem -signature yourinput.sha256 yourinputdocument