Preheat oven to 400ºF. Spread tortilla strips on a nonstick baking sheet and bake until crisp, about 10 to 12 minutes. Set aside to cool.
Meanwhile, coat a nonstick skillet with cooking spray. Add onion and cook over low heat until soft, about 5 minutes, adding a little water if onion sticks. Stir in chili powder and cumin; cook 1 minute more.
Transfer onions to a large bowl and stir in vegetable juice and vinegar. Ladle soup into 4 bowls and serve with tortilla strips. Yields about 2 cups of soup per serving. (Note: Create your own version of this soup by adding cooked, cubed chicken breasts, diced cucumbers, cilantro or fat-free sour cream. Just remember to calculate the extra POINTS®.)