Place the egg whites in a shallow dish. Place the panko in another shallow dish.
Dip the fish in egg whites; sprinkle fish evenly with 1/4 teaspoon salt, and dredge in the panko.
Heat the oil in a large ovenproof skillet over medium-high heat; swirl to coat. Add the fish to the pan; cook 3 minutes or until browned and very crispy. Turn the fish over and place the pan in the oven.
Bake the fish at 450 degrees for 7 minutes or it reaches your desired degree of doneness.
Combine the remaining 1/4 teaspoon salt, tomatoes, and remaining ingredients in a bowl. Serve with the fish.