Local lore has it that this ceviche variation from Sinaloa, in Northwest Mexico, was originally adapted by inland communities that loved scallops but couldn’t always get them. Applying a salt-and-ice brine to the more plentiful sea bass gives the fish a creamy texture that mimics the sweet flesh of scallops. But the secret of this recipe by Javier Cabral and Paola Briseño González is Sinaloa’s utterly addicting salsa negra, made with soy sauce and fresh lime juice. You’ll want to pour it over everything.
How to Make It
Arrange sea bass pieces in a large glass or ceramic bowl; sprinkle all over with salt. Gently toss until fish is evenly coated. Add ice, and fold gently with a rubber spatula until salt dissolves and ice starts to melt and pool on bottom of bowl, about 5 minutes. Cover with plastic wrap, and refrigerate until fish is firm, about 1 hour, folding gently every 15 to 20 minutes.
Whisk together lime juice, Worcestershire sauce, soy sauce, sugar, tomato paste, hot sauce, black pepper, and pequin chile in a bowl until tomato paste dissolves and ingredients are fully combined. Set dressing aside.
Thinly slice 1 cucumber to equal 1 cup, and set aside. Dice remaining cucumber to equal 1 cup, and set aside. Cut avocado in half; reserve one half for another use. Cut remaining half lengthwise into 1/4-inch-thick slices, then cut crosswise into 1/4-inch-thick slices to equal about 1 cup. Set avocado aside.
Transfer fish to a colander; discard ice. Rinse fish under cold running water. Arrange fish in a single layer on a cutting board lined with paper towels to absorb excess water; pat fish dry.
Reserve 2 tablespoons dressing. Transfer fish to a clean glass or ceramic bowl. Add red onion, diced cucumber, and remaining dressing. Stir gently to combine. Season to taste with salt and black pepper.
To serve, scoop about 1/4 cup fish mixture onto each tostada. Top evenly with sliced cucumber, avocado pieces, and a drizzle of the reserved dressing. Serve tostadas immediately.