How to Make It
In a medium saucepan, heat 1 inch of the pure olive oil to 350°. Season the fish with salt, then dredge it in the flour, turning to coat lightly. Working in batches, add the fish to the oil and fry, turning once, until golden, 4 to 5 minutes for monkfish; 3 to 4 minutes for cod. Using a slotted spoon, transfer the fish to paper towels to drain.
In a bowl, combine the onion with the cilantro, extra-virgin olive oil, lemon juice, garlic, chile and 1/2 teaspoon of salt. Arrange the fish in a single layer in a shallow glass or ceramic dish, then spoon the marinade over it and turn to coat. Let stand at room temperature for at least 1 hour. Serve immediately or refrigerate and serve cold.