1. Cut apple quarters into 1/4-inch slices. Microwave slices, 2 tsp. water, and 1 tsp. cinnamon in a microwave-safe bowl at HIGH 1 minute, stirring once. Cool 10 minutes.
2. Whisk together vinegar, sugar, mustard, salt, and remaining 1 tsp. cinnamon until well combined. Add canola oil in a slow, steady stream, whisking constantly.
3. Toss 1/2 cup vinaigrette with salad greens. Sprinkle salad evenly with goat cheese, walnuts, and apple mixture. Serve remaining vinaigrette with salad, if desired, or refrigerate up to 1 week.