Place chiles on grill rack coated with cooking spray; grill 5 minutes on each side or until blackened. Place chiles in a heavy-duty zip-top plastic bag; seal. Let stand 5 minutes. Peel chiles; cut in half lengthwise. Discard seeds and membranes. Cut chiles into 1/4-inch strips.
Place corn on grill rack coated with cooking spray; grill 10 minutes or until lightly browned, turning occasionally. Cool slightly. Cut kernels from cobs.
Combine chiles, corn, tomato, cilantro, and juice; toss gently. Add 1/2 teaspoon salt and 1/4 teaspoon black pepper.
Combine remaining 1/2 teaspoon salt, remaining 1/4 teaspoon black pepper, and cumin, stirring well. Rub spice mixture evenly over both sides of salmon. Place salmon on grill rack coated with cooking spray; grill 4 minutes on each side or until fish flakes easily when tested with a fork or until desired degree of doneness.
Serve on a bed of mixed greens with relish.