In a small bowl, whisk together the paprika, ancho chile powder, smoked paprika, cayenne, cumin, coriander, garlic powder, onion powder, oregano, and sea salt until well combined.
Season the cod generously with the blackening seasoning, reserving 1 teaspoon for the sauce. Let the fish marinate for at least 30 minutes or up to 3 hours.
In another bowl, whisk together mayonnaise, sour cream, lime juice, and the reserved seasoning until smooth. Refrigerate until ready to serve.
Heat a large nonstick skillet over medium heat and melt 1 tablespoon butter.
Cook the seasoned cod for 3–4 minutes per side until golden brown and flaky. Add additional butter as needed for remaining fillets.
Gently flake the cooked fish into large pieces.
Assemble the Blackened Fish Tacos by filling warmed corn tortillas with cod, shredded cabbage, pico de gallo, and a generous drizzle of the creamy sauce.
Serve immediately with fresh lime wedges.