Bring vinegar, ½ cup water, honey, and 1 teaspoon salt to a boil in a small saucepan. Add onion to a medium bowl. Pour boiling vinegar mixture over onion mixture and let sit at least 15 minutes.
Combine 1 tablespoon paprika, cumin, oregano, remaining teaspoon salt, black pepper, and cayenne in a shallow bowl.
Pat fish fillets dry then coat fillets in spice mixture on all sides; rubbing in as needed.
Heat a large cast-iron skillet or nonstick skillet set over medium for 3 minutes. Add 1 tablespoon of oil to skillet, swirl to coat, then add 2 fish fillets. Cook fillets just until starting to blacken, about 4 minutes. Flip the fillets and cook 3–4 minutes more until blackened on second side and a thermometer inserted in the thickest parts registers between 140ºF and 145ºF; transfer to a plate.
Repeat cooking process with remaining oil and fillets.
Combine mayonnaise, yogurt, 1 tablespoon lime juice, 1 teaspoon lime zest, and ½ teaspoon paprika; season with salt and pepper to taste.
Using tongs, char tortillas over an open flame on the stove top, turning frequently to char all over.
Serve blackened fish in charred tortillas with arugula, black beans, pickled onions and sauce. Finish with a squeeze of lime and fresh cilantro.