How to extract the RSA public key from a .cer and store it in a .pem using OpenSSL?

Using this command I was able to generate the .pem with the contents of the public key.

openssl x509 -inform der -in certificate.cer -pubkey -noout > certificate_publickey.pem

Which produces:

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCsM+whXrxmbCkPfkwY2EehYpIp
*blah blah blah blah*
-----END PUBLIC KEY-----