1. Combine yogurt, garlic powder, ginger, coriander seeds, cumin, paprika and salt in small bowl. Spread 1/3 cup of mixture over steak. Reserve remaining yogurt mixture for sauce. Marinate steak in refrigerator for 6 hours or as long as overnight.
2. Remove steak from marinade; discard marinade. Place steak on grid over medium, ash-covered coals. Grill, covered, 11 to 16 minutes (over medium heat on preheated gas grill, covered, 16 to 21 minutes) for medium rare (145°F) to medium (160°F) doneness, turning occasionally. Meanwhile, grill onion slices, covered, 11 to 15 minutes. Remove steak from grill; let stand 3 to 5 minutes.
3. Meanwhile, heat remaining sauce in small saucepan over medium heat 2 to 3 minutes. Cut steak lengthwise in half, then across the grain into thin slices. Cut onions into bite-sized pieces. Combine rice and peas in large bowl. Divide rice mixture evenly among plates. Serve with beef, onions and sauce.