To achieve this task, you need to perform the following steps:

1. Read the GeoJSON file.
2. Extract the polygon coordinates and field name.
3. Format the data according to the Farmonaut system's requirements.
4. Submit the formatted data to the specified API endpoint.

Here's a Python function that accomplishes these steps:

```python
import json
import requests

def submit_geojson_to_farmonaut(geojson_data):
    # Constants
    UID = "qbnmIkSbAwc8TTR5FPnViu2Rr0A2"
    CropCode = "1r"
    PaymentType = 1
    API_URL = 'https://us-central1-farmbase-b2f7e.cloudfunctions.net/submitField'
    
    # Iterate over each feature in the geojson
    for feature in geojson_data['features']:
        # Extract field name
        field_name = feature['properties']['name']
        
        # Extract polygon coordinates & ensure it is in the correct format
        if feature['geometry']['type'] == 'Polygon':
            coordinates = feature['geometry']['coordinates'][0]
        
        # Prepare the request body
        request_body = {
            "UID": UID,
            "CropCode": CropCode,
            "FieldName": field_name,
            "PaymentType": PaymentType,
            "Points": coordinates
        }
        
        # Submit the request to the API
        response = requests.post(API_URL, json=request_body)
        if response.status_code == 200:
            print(f"Successfully submitted field: {field_name}")
        else:
            print(f"Failed to submit field: {field_name}. Status Code: {response.status_code}, Response: {response.text}")

def read_geojson_file(file_path):
    with open(file_path, 'r') as file:
        geojson_data = json.load(file)
    return geojson_data

if __name__ == "__main__":
    # Provide the path to your GeoJSON file
    geojson_file_path = 'path/to/your/geojson/file.geojson'
    
    geojson_data = read_geojson_file(geojson_file_path)
    submit_geojson_to_farmonaut(geojson_data)
```