What is the semantically correct way to use a PUT request to update a record?

Question

Web development

For example, there is a large document, on the server, in JSON format, which needs to be updated via the API. And you only need to update 1 parameter.
How to compose the body of a PUT request?

{
    key: "name",
    value: "A new name"
}

Or

{
    name: "A new name"
}

Or somehow else?