Pat fish dry with paper towels. Arrange in an 8-inch square glass baking dish so that pieces are toward the sides of dish. Combine salsa, tomatillos, cilantro, lime juice and coriander. Spoon mixture over fish. Cover with vented plastic wrap. Rotating dish midway through cooking, microwave on high 3 to 4 minutes, or just until fish flakes easily when tested with a fork. Serve on a heated tortilla garnished with sprigs of cilantro.
