Make the creamy cilantro sauce. Place all the ingredients in a food processor or blender and blend until combined. Taste the sauce. You may need to add some water to thin it out. Refrigerate until needed.
Make the blackening seasoning. Mix the spice mixture in a bowl. Liberally coat the fish with the spice mixture. Drizzle the fish with olive oil then bake for 12-15 minutes, until just cooked through and flakey.
While the fish is cooking, warm the tortillas. You can either do this right on the stovetop or in the microwave.
To make the tacos- Place about 1/4 cup halibut in the warm tortillas. Add a couple tablespoons of cabbage to each taco then drizzle with the cilantro sauce. Top each taco with cilantro and serve with a squeeze of lime. Enjoy!