Season the fish on both sides with cumin, chili powder, and salt; set aside.
Prep the sauce and the slaw. Whisk sour cream or Greek yogurt, juice of 1/2 lime, water, chili powder, and salt together in a small bowl. Toss slaw ingredients together in a medium bowl. Place both in the fridge until ready to eat.
Cook the fish. Drizzle olive or avocado oil in a large skillet over medium-high heat. When hot, place fish in the skillet and cook for 4-5 minutes on each side, just until the fish is cooked through and blackened in spots. Remove fish from the skillet, spritz with lime juice, and break apart into large chunks.
Assemble the tacos, starting with the charred or warmed tortilla and layering on slaw, fish, and sauce, in that order. Add avocado or other toppings, as desired, and serve with extra lime wedges.
Notes
Adobo sauce is most easily found in a small can accompanying chipotle chili peppers, which you can usually find near other Mexican foods in major grocery stores. If you don’t have any, leave it out and stir 1/2 teaspoon chili powder into the sauce, instead.
This yields between 8-12 tacos, depending on how large and how full your tortillas are. Nutritional estimate is per 2 generous tacos, or 1/4 of the recipe, but will vary depending on the type of tortillas and other toppings used.