Thaw fish, if frozen. Rinse fish; pat dry with paper towels. Cut fish into 4 serving-size pieces.
In a shallow bowl combine the flour, sesame seeds, and pepper. Transfer 2 tablespoons of the salad dressing to a small bowl. Brush all sides of the fish pieces with the 2 tablespoons salad dressing. Firmly press both sides of each fish piece into sesame mixture.
In a 12-inch skillet heat oil over medium heat. Cook coated fish in hot oil about 6 minutes or until fish flakes easily when tested with a fork, turning once.
Divide spinach mixture among 4 dinner plates; top each with a fish piece. Drizzle with the remaining salad dressing. Makes 4 servings.