Removing backslash from JSON by returing Content

Entity Framework children serialization WebAPI

public class Contact
{
    public int Id { get; set; }
    public string UserName { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    ...
        
    //[JsonIgnore]
    //[JsonProperty("notificationContact")]
    public List<NotificationContact> NotificationContact{get; set;}
}
public class NotificationContact
{
    public int Id { get; set; } 
    public int ContactId { get; set; }
    //[JsonIgnore]
    public Contact Contact { get; set; }

    public int NotificationId { get; set; }
    //[JsonProperty("notification")]
    public Notification Notification {get;set;}     

}
public static class ContactSerialize
{
    public static string ToJson(this Contact self) => JsonConvert.SerializeObject(self,Converter.Settings);
}

public class Converter
    {
        public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
        {
            MetadataPropertyHandling = MetadataPropertyHandling.Ignore,
            DateParseHandling = DateParseHandling.None,
            Formatting = Formatting.Indented, 
            ReferenceLoopHandling = ReferenceLoopHandling.Ignore, 
            ContractResolver = new CamelCasePropertyNamesContractResolver()
         };
 }
 
 
 [HttpGet("{id}")]
        public async Task<IActionResult> GetContact([FromRoute] int id)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            var contact = await _context.Contact
                .Include("NotificationContact.Notification")
                .Include("UserContactTypeContact.ContactType")
                .Include("Address")
                .SingleOrDefaultAsync(m => m.Id == id);

            if (contact == null)
            {
                return NotFound();
            }
            return Content(contact.ToJson());
            //return contact;
        }
        
        
///Output
{
  "id": 3031,
  "userName": null,
  "firstName": "..",
  "lastName": "..",
  "email": "..",
  "irs": "..",
  "portCode": null,
  "selfFilerCode": "..",
  "achCode": "..",
  "picPath": null,
  "address": {
    "id": 4028,
    "street": "77 Turner St Middlesex County",
    "addressPart1": null,
    "addressPart2": null,
    "city": "Woodbridge Township",
    "state": "New Jersey",
    "zip": "07064",
    "country": "United States"
  },
  "notificationContact": [
    {
      "id": ..,
      "contactId": ..,
      "notificationId": 3,
      "notification": {
        "id": 3,
        "description": "SMS"
      }
    }
  ],
  "userContactTypeContact": [
    {
      "id": ..,
      "userId": 4,
      "user": null,
      "contactId": 3031,
      "contactTypeId": 8,
      "contactType": {
        "id": 8,
        "description": "Chat"
      }
    },
    {
      "id": 4105,
      "userId": 4,
      "user": null,
      "contactId": 3031,
      "contactTypeId": 7,
      "contactType": {
        "id": 7,
        "description": "Stuffer"
      }
    }
  ],
  "userId": 4,
  "user": null
}