Sending Nested Array in JSON Format

Hey everyone,

Take a look at this image please -> https://ibb.co/2ZhvSC6

How can I setup the fields so the sent format would be the following instead?

{
    "email": "[email protected]",
    "customFields": [
      {
        "key": "InviteCode",
        "value": "ABC123"
      }
    ]
}

Thanks all!