Peel and cut the potatoes lengthwise into ½-inch thick slices; cut the slices into ½-inch-thick sticks.
In a large bowl, toss the potatoes with oil and pepper. Transfer to a 15x10x1-inch baking pan coated with cooking spray. Bake, uncovered, 25 to 30 minutes or until golden brown and crisp, stirring once.
Meanwhile, in a shallow bowl, mix the flour and pepper. In another shallow bowl, whisk the egg with water. In a third bowl, toss the cornflakes with cheese and cayenne. Dip the fish in the flour mixture to coat both sides; shake off the excess. Dip in the egg mixture, then in the cornflake mixture, patting to help the coating adhere.
Place the coated fish on a baking sheet coated with nonstick spray. Bake 10 to 12 minutes or until the fish just begins to flake easily with a fork. Serve with the fries, tartar sauce and lemon wedges.
Notes
Air Fryer Variation: Preheat the air fryer to 400 degrees F. In batches, place the potatoes in a single layer on a greased tray in the air-fryer basket; cook until just tender, 5 to 10 minutes. Toss the potatoes to redistribute; cook until lightly browned and crisp, 5 to 10 minutes longer.
Meanwhile, season and coat the fish.Remove the fries from the basket; keep warm. Place the fish in a single layer on a greased tray in the air-fryer basket. Cook until the fish is lightly browned and just beginning to flake easily with a fork, 8 to 10 minutes, turning once halfway through cooking. Do not overcook. Return the fries to the basket to heat through if necessary.