Make the pickled onions first so they have a little time to soften. Combine the sliced red onion, salt, vinegar, and hot water in a jar or bowl and give it a quick stir. Let them sit while you prepare the rest of the tacos.

In a small bowl, stir together the mayonnaise, sour cream, garlic, smoked paprika, lime juice, salt, and sugar until smooth. Taste and adjust the lime or salt if needed.

Heat olive oil and butter in a skillet over medium heat. Season the fish with salt and pepper, then cook for a few minutes on each side until the fish is golden on the outside and flakes easily with a fork.

Warm the tortillas in a skillet until lightly toasted.

Spread some of the lime sauce onto each tortilla, then add the cooked fish. Top with shredded cabbage, black beans, corn, and a few pickled onions.

Finish with an extra drizzle of sauce and a squeeze of fresh lime before serving.