1. Stir together the yogurt, mayonnaise to make a sauce.
2. Mix cabbage, onions and cilantro with half of the yogurt sauce.
3. Prepare fish according to package directions. Place over warm tortillas.
4. Top with cabbage mixture and radishes. Serve with remaining yogurt sauce.
Tip: For a hint of heat and extra flavor add sliced jalepeno peppers, and a sqeeze of fresh lime juice