Preparation

• Finely grate the zest from 1 medium lime into a medium bowl. Add 1 tablespoon of the vegetable oil, 1 ¼ teaspoons of the kosher salt, 1 teaspoon chili powder, ½ teaspoon smoked paprika, and ½ teaspoon garlic powder and stir to combine.
• Cut 1 ½ pounds mahi-mahi into 1 ½ 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.
• 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 food processor. Cut any remaining lime into wedges for serving.
• 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.
• Trim and halve 1 small jalapeño crosswise. Scrape the seeds from one half and add to the food processor. Cut the remaining half into thin rounds for serving.
• Add 1 garlic clove, ¼ cup sour cream, and the remaining ½ teaspoon kosher salt to the food processor. Process until very smooth, about 1 to 2 minutes, scraping down the bottom and sides as needed. Transfer to a large bowl.
• Core and very thinly slice ½ small head red cabbage until you have 4 cups. Add to the avocado dressing and toss until coated. Taste and season with more kosher salt as needed.
• Warm 8 (6- to 8-inch) corn or flour tortillas one at a time by holding them directly over a medium flame or in a skillet over medium heat, flipping occasionally, until charred in spots and pliable.
• 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. Cook undisturbed until browned, about 3 minutes. Flip and cook until browned and cooked through, about 2 to 3 minutes. Transfer to a clean plate.
• Assemble the tacos: Peel and dice the remaining avocado half. Divide the mahi-mahi and slaw among the warmed tortillas. Garnish with the avocado, jalapeños, and optional toppings. Serve with lime wedges.