Fried Fish Sandwich with Pepper Slaw

Name: Fried Fish Sandwich with Pepper Slaw
Ingredients: 1 tablespoon plus 1 1/2 teaspoons fresh lemon juice; 1 tablespoon plus 1 1/2 teaspoons fresh lime juice; 1 tablespoon hot sauce; 1 tablespoon olive oil; 1/2 teaspoon dried oregano; 1/2 teaspoon kosher salt; 1/2 medium white onion, thinly sliced; 1 large jalapeño, thinly sliced, seeds removed; 1/2 medium poblano chile, thinly sliced, seeds removed; 6–7 cornichons, thinly sliced into 1/4 coins; 1/2 cup mayonnaise; 1/4 cup coarsely chopped fresh parsley; 3 teaspoons coarsely chopped capers; 2 teaspoons tomato powder (optional); 1 1/2 teaspoons distilled white vinegar; Large pinch chili powder; Large pinch kosher salt; 1 cup all-purpose flour; 1 cup cornstarch; 3 teaspoons dried oregano; 2 teaspoons onion powder; 1 teaspoon garlic powder; 3 teaspoons kosher salt, plus more; 1 1/2 cups club soda; Canola oil (for frying); 4 (4 1/2-ounce) skinless black bass fillets; 4 sesame seed potato buns, split, toasted; 8 slices ripe tomato