Ingredients:

• For the pickled onion
• 1/3 cup apple cider vinegar
• 1 tablespoon sugar
• 1 teaspoon kosher salt
• 1/2 medium red onion, thinly sliced
• For the fish sandwiches
• 1 1/4 pounds firm white fish such as halibut, cod, or grouper
• 1 1/4 teaspoons kosher salt, divided
• 1/4 teaspoon ground black pepper
• 1 cup panko style breadcrumbs
• 1 tablespoon garlic powder
• 1 tablespoon ground cumin
• 2 large eggs
• 1/4 cup all-purpose flour
• Non-stick cooking spray
• For the avocado mayo
• 1 large ripe avocado, peeled and pitted
• 1 tablespoon lime juice
• 2 tablespoons mayonnaise
• To serve
• 4 soft sandwich buns, such as brioche
• 2 cups romaine hearts, shredded
• 2-3 tablespoons pickled jalapenos