Preheat oven to 200 degrees Celsius (390 Fahrenheit).

In a small bowl, whisk together the olive oil, lemon juice, paprika, cumin, sumac, salt, and chili powder (if using). Place fish in a shallow baking dish and brush seasoning mixture over it until well coated.

Bake for 12 minutes. Flake the fish with a fork.

To a large container, add the green cabbage, purple cabbage, cilantro, scallions, jalapeños (if using), lemon juice, olive oil, honey, salt, and pepper. Seal the container and shake to combine.

If you like, heat the tortillas on a grill pan until they have grill marks.

Fill the tortillas with slaw and top with flaked fish. Squeeze a lime wedge over the top and add a couple of cilantro leaves and avocado slices (if using). Crumble about one and a half tablespoons of feta onto each taco.