Method:
Preheat oven to 425°F. Arrange fish in a single layer on a baking sheet lined with parchment paper. In a small bowl, mix cumin, salt and cayenne, if using. Sprinkle evenly over both sides of fish. Bake until golden brown and flesh begins to flake, 9 to 11 minutes. Transfer fish to a medium bowl, toss with lime juice and break into small pieces. Fill warmed taco shells with fish, lettuce, tomato and green onions and top with shredded cheese.