In a small bowl, mix together the chili powder, paprika, ground cumin, garlic powder, onion powder, black pepper, salt, and cayenne pepper. Rub the spice mixture evenly over both sides of the cod.

Heat olive oil and butter in a large skillet over medium-high heat until sizzling. Add the seasoned fish and cook for 4-5 minutes until charred, then flip and cook for another 4-5 minutes until opaque and flaky.

In a medium bowl, combine shredded cabbage, lime juice, and chopped cilantro. Season with salt and black pepper to taste and toss until evenly coated.

In a small dish, whisk together mayonnaise, sriracha, sugar, and a pinch of salt until smooth. Adjust sriracha according to preference.

To assemble, place fish in the center of a tortilla, top with slaw and drizzle with sriracha mayo. Fold and serve immediately, garnished with lime wedges.