Step 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.

Step 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.

Step 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.

Step 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.

Step 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.

Step 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.

Step 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.

Step 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.

Step 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.

Step 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.