To prepare salsa, remove husks and stems from tomatillos. Place tomatillos and onion, cut sides down, on a baking sheet coated with cooking spray. Broil 10 minutes or until tomatillos begin to blacken. Place tomatillos, onion, 1/2 cup cilantro, and next 4 ingredients (1/2 cup cilantro through jalapeño) in a food processor; process until pureed. Pour salsa into a bowl; cool completely.
Preheat oven to 350°.
To prepare tacos, wrap tortillas in foil; bake at 350° for 10 minutes or until thoroughly heated; keep warm.
Sprinkle fish with 1/4 teaspoon of salt. Combine 1/4 teaspoon salt, flour, and cumin in a medium bowl; dredge fish in flour mixture.
Heat oil in a large nonstick skillet over medium-high heat, and add fish. Cook 2 minutes on each side or until fish flakes easily when tested with a fork. Place 2 pieces of fish down center of each tortilla; top each taco with 2 teaspoons cilantro, 1 tablespoon onion, and 1 tablespoon avocado. Fold tacos in half; serve with salsa.