Red bell pepper slices Paprika Trim fat from boneless beef sirloin steak;cut steak into 1 1/2 inch pieces.Mix brown sugar,vinegar,oil,chili powder,salt and hot pepper sauce in medium bowl.Add beef pieces;toss to coat.Let stand 15 minutes.Meanwhile,stir together yogurt,green onions and garlic salt;set aside.Wash spinach;discard stems and pat dry. Coarsely chop spinach;set aside.Thread beef pieces on 6 to 8 9 inch skewers.Place beef on grill over medium coals.Grill beef 8 to 10 minutes,to desired doneness,turning frequently. To serve,place spinach around edge of large serving platter leaving center open for small serving bowl.Remove beef from skewers and arrange over spinach.garnish beef with peppers.Put yogurt sauce in serving bowl;sprinkle with paprika.Place bowl in center of platter.Serves 6 to 8.