Puree the cranberries in a food processor until smooth. Add the vinegar, onion, sugar and mustard and process until well blended. With the processor running, gradually add the oil and process until well blended.
Transfer the vinaigrette to a medium bowl. Season to taste with salt and pepper. (Can be made 1 day ahead. Cover; chill. Bring to room temperature and whisk before using).
ASSEMBLE THE SALAD:
In a large bowl, combine the greens and apples. Toss with enough dressing to coat. Sprinkle with walnuts. Add goat cheese, if using.
Serve, passing remaining dressing separately.
Notes
You will only need about half the vinaigrette for the salad. Save the rest for another day.
WW Points are calculated using half the vinaigrette and none of the optional cheese.