Preheat the oven to 450F or 425F convection. Line a baking sheet with parchment paper.
To make the sauce, add all ingredients to a high-speed blender and blend until smooth. If it’s not blending easily, add a splash of water.
Add 5-6 cups cabbage to the baking sheet along with 2 tablespoons oil and ½ teaspoon salt. Toss to coat then spread out into an even layer. Bake for about 15-20 minutes, or until beginning to get charred and tender.
Meanwhile, in a small bowl mix together your spice mixture and the remaining ½ teaspoon salt. Sprinkle it all over the fish and drizzle the remaining 1 tablespoon oil over top. Use your hands to spread everything all around to coat the fish.
Place the fish on top of the cabbage, then return to the oven for 10-15 more minutes or until the fish is cooked through (flakes easily with a fork)(the cabbage should be nicely charred at this point!).
Transfer the fish to a plate or cutting board and flake it up. Add the remaining 2-3 cups cabbage to the baking sheet and toss with the cooked cabbage.
Warm your tortillas and top with the cabbage and fish. Scatter the orange chunks along the taco, if using. Spoon the sauce generously over top and garnish with cilantro and pickled red onions (if using).