Preheat oven to 375°F.
Cut fillets in 8 roughly even-size pieces.
In a medium bowl, crush cornflakes.
In a second medium bowl, mix flour, salt, and black pepper.
In a third medium bowl, add eggs and milk. Beat with a fork.
Dip each fish piece into flour, then egg mixture, then cornflakes. Each piece should be fully coated with flakes.
Coat baking sheet with non-stick cooking spray. Place fish pieces on sheet, evenly spaced. Spray pieces lightly with cooking spray.
Bake until fish flakes easily with a fork, about 15-20 minutes. While fish cooks, prepare tartar sauce.
Rinse lemon. In a small bowl, squeeze juice. Discard seeds.
In a second small bowl, add mayonnaise and yogurt. Whisk with a fork until smooth. Add relish, black pepper, and 2 teaspoons lemon juice. Stir until combined.
When fish cooked, serve immediately. Add a dollop of tartar sauce on top or serve on the side.