Combine shredded cabbage and salt in a medium bowl and toss well.
Add red onion, chopped cilantro, jalapeño, lime juice, and olive oil to the cabbage and mix thoroughly adjusting seasoning to taste.
Prepare your preferred fish taco sauce such as Chipotle Mayo ahead of time if possible.
Heat your grill to medium-high or preheat oven to 400°F.
Pat the fish dry and in a small bowl mix chili powder, cumin, coriander, granulated garlic, kosher salt, sugar, chipotle powder, and smoked paprika if using.
Lightly coat all sides of the fish with the spice rub and let it rest.
For grilling, oil the grate well and cook fish on medium heat few minutes per side until opaque and flaky, then squeeze lime juice over.
To bake, place fish on a parchment-lined pan, spray with olive oil, bake 6 minutes, flip, spray again with olive oil, then bake another 4-6 minutes until cooked through and flaky; squeeze lime juice.
For pan-searing, heat olive oil over medium-high heat, sear fish 3-4 minutes each side until golden and cooked through finishing with a squeeze of lime juice.
Warm tortillas by lightly grilling on the grill, placing directly on the oven rack, or over a gas flame.
Assemble tacos by placing cooked fish onto tortillas, topping with the cilantro lime cabbage slaw and garnishes like avocado slices, Cotija cheese, extra cilantro, and drizzle with chipotle mayo or your chosen sauce.
Serve immediately and enjoy.