In small bowl, combine vegetable juice cocktail, balsamic vinegar, honey, olive oil, chili powder, ground cumin and salt; remove 1/2 cup dressing and reserve. Place remaining mix in airtight container and reserve for other uses (enough for about 2 batches salad).
In large bowl, combine beans, tomato and onion; mix well. Add 1/2 cup reserved dressing; toss to coat. Add spinach; toss to coat.