Prepare the spice rub by combining chili powder, paprika, ground cumin, garlic powder, onion powder, black pepper, salt, and cayenne pepper in a small bowl.

Heat 2 tablespoons of olive oil and 1 tablespoon of unsalted butter in a cast-iron skillet over medium-high heat until shimmering.

Cook the seasoned cod for 4-5 minutes on one side, then flip and cook for another 4-5 minutes until flaky.

For the cilantro slaw, mix 2 cups of shredded cabbage, juice of 1 lime, ¼ cup of chopped cilantro, and a pinch of salt and black pepper in a bowl.

Whisk together ½ cup of mayonnaise, juice of a lime, 2 tablespoons of sriracha, and 1 teaspoon of sugar until smooth for the sriracha mayo.

Warm the tortillas in a dry skillet, then assemble each taco with fish, slaw, and sriracha mayo.