Soak the wood plank in water to cover for 1 hour, then drain. (It's actually best if you can soak it for several hours).
Prepare the grill, heating one side to medium heat (300℉ to 350℉) and one side to high heat (400℉ to 500℉).
MAKE THE CITRUS SLAW:
In a large bowl, combine the cabbage with green onions, sour cream, lime juice and salt; toss well to coat. Chill.
MAKE THE TACOS:
In a small bowl, combine the chili powder, cumin, pepper, and salt. Sprinkle the chili powder mixture over the halibut fillets.
Place the plank on the grill grate over high heat; grill 5 minutes or until lightly charred. Carefully turn the plank over; move to medium heat. Place the fish on the charred side of the plank. Grill the halibut, covered with the grill lid, about 18 minutes or until the fish flakes easily with a fork.
Warm the tortillas according to package directions. Break the fish into chunks, and place about 2 ounces of fish on each tortilla. Top each taco with ¼ cup slaw, and garnish with avocado and cilantro.
Notes
Use low fat tortillas to make this a lower fat meal. Use low carb tortillas to make this a lower carb meal!
If preparing this recipe as GLUTEN FREE, just be sure to use GF corn tortillas (in place of flour).