In a large bowl toss together cabbage, jicama, and green onion. Set aside.
Using a mini food processor or blender puree together avocado, sour cream, mayonnaise, lime juice, lime zest, onion powder, salt and pepper until smooth. Add cilantro and pulse until cilantro is coarsely chopped and combined.
Combine shredded cabbage mixture with just enough dressing to coat the salad well. Serve immediately.
Add dressing to salad just before serving to maintain optimum freshness and crunch. Save any additional dressing to drizzle over tacos or spread on your favourite sandwich or hamburger.