Preheat broiler. Line a large rimmed baking sheet with nonstick foil, or line with regular foil and coat with cooking spray (or just coat with cooking spray, if you prefer).
Place steak and peppers on prepared pan; coat with cooking spray.
In a small cup, combine cumin, oregano and salt; sprinkle on both sides of steak and peppers.
Broil 3 to 4 inches from heat, turning peppers and steak halfway through cooking, about 4 to 5 minutes per side for medium-rare, or longer until desired degree of doneness. Remove steak to a cutting board; let stand 5 minutes.
Meanwhile, put cilantro, salsa and sour cream in blender or food processor; process until smooth.
Slice steak thinly across the grain. Put steak and peppers on a serving platter and serve with salsa mixture. Yields about 2 1/2 ounces steak, 3 pieces pepper and 1/4 cup salsa mixture per serving.