Entity Framework: How to perform the Insert of a table with relation 1.. n without the children also being inserted?

Question

I am using Dotnet Core 3.1 with EF Core. I have three classes in my context:

public class Sale
{
    public Sale()
    {
        this.Cars = new List<Car>();
        this.CarSeller = new Seller();
    }

    [Key]
    public int Id { get; set; }
    [Required]
    public DateTime Date { get; set; }
    [Required]
    public ProcessStatusEnum Status { get; set; }
    [Required]
    public Seller CarSeller { get; set; }
    public virtual List<Car> Cars { get; set; }

}

public class Car
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string Brand { get; set; }
    [Required]
    public string Type { get; set; }
    [Required]
    public int Year { get; set; }
    [Required]
    public string Fabrication { get; set; }
    public Sale Sale { get; set; }

}

 public class Seller
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public string Cpf { get; set; }
    [Required]
    public string Email { get; set; }

}

My doubt is occurring when I try to insert a new sale:

 public ActionResult<int> SaveVehicleSale(SaleDTO newSale)
    {
        try
        {
            newSale.Id = 0;
            newSale.Status = ProcessStatusEnum.ConfirmingPayment;

            if (Functions.IsAnyNullOrEmpty(newSale))
                new ApiException(StatusCodeEnum.BadRequest, MsgException.ObjectAtributeNull);

            _context.Sale.Add(ConvertType.To(newSale)); //Converte o SaleDTO para o Sale
            _context.SaveChanges();

            return _apiResponse.ResponseRet<int>(StatusCodeEnum.OK, newSale.Id);
        }
        catch (ApiException e)
        {
            return _apiResponse.ResponseRet<int>(e);
        }
        catch (Exception e)
        {
            return _apiResponse.ResponseRetWithoutEnumerable(e);
        }
    }

When entering, it is also trying to add a new Car. How do I make it just reference an existing car? This already happens with the Seller Class, but I don’t know how to do it with a List type<>.

Thank you very much, from now on!