POST request to a model with a nested serializer Django rest framework

i have a Product model that has a many-to-one relationship with a Brand model

class Product(models.Model):
    name = models.CharField(max_length=200)
    description = models.CharField(max_length=500)
    sku = models.CharField(max_length=50)
    upc = models.CharField(max_length=12, blank=True)
    asin = models.CharField(max_length=10, blank=True)
    brand = models.ForeignKey(
        Brand,
        on_delete=models.CASCADE,
        null=True,
    )
    # buybox = models.FloatField(blank=True)
    vendors = models.ManyToManyField(Vendor, blank=True)
    added = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.name + ": " + self.description

Brand model

class Brand(models.Model):
    name = models.CharField(max_length=50)

    def __str__(self):
        return self.name

and a nested serializer

class ProductSerializer(serializers.ModelSerializer):
    brand = BrandSerializer(required=False, read_only=True)

    class Meta:
        model = Product
        fields = "__all__"

when i make a POST request to add a new product to my table i keep getting errors and i cant figure out how to structure the json that is getting sent

the only way i can get it to not give an axios error is if i send the following JSON but when i do, the product that gets added to the database has the brand set as NULL

{
  "name": "examplename",
  "description": "example desc",
  "sku": "SKUSKUSKU",
  "asin": "ASINASIN12",
  "price": "11.11",
  "brand": {
    "id": 1,
    "name": "Honeywell"
  }
}

here is the function that sends the request

function addProduct(product) {
    // axios post request for a new product
    console.log(product)
    axios.post("http://127.0.0.1:8000/products/", product)
        .then((response) => {
            console.log(response);
            alert("Success");
            reset('productForm')

        })
        .catch((error) => {
            console.log(error);
            alert(error);
        })
}

when posting data to a model that has a relationship, do i have to send the id (primary key) of the "brand" in this case or do i send the whole brand object nested in the JSON?

what am i doing wrong?

EDIT:
heres the correct JSON that i get when doing a GET request of a single product that was created manually from the django admin page

{
        "id": 9,
        "brand": {
            "id": 2,
            "name": "Beano"
        },
        "vendors": [],
        "name": "beans",
        "description": "big ol can o beans",
        "sku": "beansbeansbeans",
        "upc": "",
        "asin": "bB00nvn",
        "added": "2022-12-28T19:09:30.007480Z",
        "updated": "2022-12-28T19:09:30.013781Z"
    }

i think you have to override the default create() method in the serializer