Web API: GetOne return object json

I've created a WEB API project with EMPTY template. I would like the GetOne () method to return a json object but it is returning an json array. Why?

I would like it to return:

{"Id": 1, "Nome":"Jhon"}

But it's returning:

[{"Id": 1, "Nome":"Jhon"}]

My controller looks like this:

public class PessoaController : ApiController
{
      private DataModel db = new DataModel();

      public IHttpActionResult GetOne(int id) => Ok(GetPessoa(id));

      private IQueryable GetPessoa(int id)
      {
          var pessoa = (from f in db.Pessoas
                     where f.Id == id
                      select new
                      {
                          Id = f.Id,
                          Nome = f.Nome
                      });
          return pessoa;
      }

  }
}

WebApiConfig.cs looks like this:

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));

config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );