1. Mix half the lime juice, 1/2 cup mayo, dressing mix and mustard in medium bowl until blended. Add crabmeat, 1/2 cup cracker crumbs and onions; mix lightly.
2. Shape into 18 (1/2-in.-thick) patties; coat with remaining cracker crumbs.
3. Cook, in batches, in large nonstick skillet on medium heat 2 min. on each side or until browned on both sides and heated through. Meanwhile, mix sour cream, lime zest, remaining mayo and lime juice.
4. Serve crab cakes with lime sauce.