Easy Fish Tacos With Spicy Sauce

Name: Easy Fish Tacos With Spicy Sauce
Ingredients: 1 cup sour cream or plain whole-milk Greek yogurt; 2 Tbsp. sriracha; 1 Tbsp. fresh lime juice; 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt; ¼ tsp. sugar; ¼ small head of cabbage, thinly sliced; 2 Tbsp. fresh lime juice; 3 Tbsp. extra-virgin olive oil, divided; 3 tsp. Diamond Crystal or 1¾ tsp. Morton kosher salt, divided; 1 Tbsp. ground cumin; 1 Tbsp. paprika; ½ tsp. cayenne pepper; 1½ lb. skinless, boneless cod or halibut fillets; Warm small corn tortillas, thinly sliced red onion, thinly sliced jalapeño, cilantro leaves with tender stems, and lime wedges (for serving)