Cajun Tilapia PoBoy for Two

Name: Cajun Tilapia Po'Boy for Two
Ingredients: 1 large tilapia fillet (6-7 ounces); 1 teaspoon Cajun spice blend (without added salt); ¼ teaspoon salt; 1 egg white; 2 tablespoons water; ¼ cup fine cornmeal; 1 tablespoon canola oil, divided; 2 ½ tablespoons low-fat mayonnaise; 1 ½ tablespoons finely chopped dill pickle; 2 small whole-wheat hoagie buns (2-3 ounces each), toasted; 1 ripe plum tomatoes, sliced; ¼ cup thinly sliced red onion; 1 cup very thinly sliced romaine or iceberg lettuce