Instructions

1. Finely grate the zest from 1 medium lime (about 2 teaspoons) into a medium bowl. Add 1 tablespoon of the vegetable oil, 1 1/4 teaspoons of the kosher salt, 1 teaspoon chili powder, 1/2 teaspoon smoked paprika, and 1/2 teaspoon garlic powder and stir to combine.
2. Cut 1 1/2 pounds mahi-mahi into 1 1/2 to 2-inch pieces. Add to the spice mixture and toss to coat. Set aside for about 15 minutes while you prepare the avocado sauce and slaw.
3. Clean the cutting board. Juice the zested lime until you have 2 tablespoons, juicing the second lime as needed, and pour into the bowl of a regular or mini food processor fitted with the blade attachment. Cut any remaining lime into wedges for serving.
4. Halve and pit 1 ripe medium avocado. Scoop the flesh from one half into the food processor. Place the remaining avocado half cut-side down until ready to serve.
5. Trim and halve 1 small jalapeño crosswise. Scrape the seeds from one half, if desired, for a mild sauce, then add to the food processor. Cut the remaining half into thin rounds for serving.
6. Add 1 garlic clove, 1/4 cup sour cream, and the remaining 1/2 teaspoon kosher salt to the food processor. Process until very smooth, 1 to 2 minutes, scraping down the bottom and sides of the bowl as needed. Transfer to a large bowl.
7. Core and very thinly slice 1/2 small head red cabbage until you have 4 cups. Add to the avocado dressing and toss with tongs until coated. Taste and season with more kosher salt as needed.
8. Warm 8 (6- to 8--inch) corn or flour tortillas one at a time by holding them directly over a medium flame on a gas stove, or in a skillet over medium heat on an electric stove, flipping occasionally, until charred in spots and pliable. (Alternatively, wrap the stack of tortillas in a damp paper towel and microwave until warm, 20 to 25 seconds.) Stack together and wrap in a clean kitchen towel or aluminum foil to keep warm.
9. Heat 1 tablespoon of the vegetable oil to a large nonstick skillet over medium heat until shimmering. Add half of the mahi-mahi in a single layer, making sure not to overcrowd the pan. Cook undisturbed until the fish is browned and releases easily from the pan, about 3 minutes. Flip the fish and cook on the second side until browned and releases easily from the pan, and the fish is cooked through, 2 to 3 minutes. Transfer to a clean plate. Repeat cooking the remaining mahi-mahi in the remaining 1 tablespoon vegetable oil.
10. Assemble the tacos: Peel and dice the remaining avocado half. Divide the mahi-mahi and slaw evenly among the warmed tortillas. Garnish with the avocado, jalapeños, and other optional toppings, if desired. Serve with the lime wedges for squeezing.