Preheat the oven to 400 degrees F. Wrap the beets individually in tin foil and roast directly on the rack in the oven until tender, about 1 hour. Open the foil packets and let cool. Once they're cool, peel the beets and cut into small chunks.
In a large bowl, whisk together the olive oil, vinegar, honey, red onion, and mustard. Season with salt and pepper. Add the beets and spinach to the dressing and toss to coat. Transfer the salad to a platter or plates, top with the goat cheese and walnuts, and serve.
Recipe from "Farmhouse Rules" by Nancy Fuller. Copyright (c) 2015 by Fuller Farms, LLC. Used with permission by Grand Central Life & Style. All rights reserved.