1. Lightly grease 4 sheets of aluminum foil and place a fish fillet in the center of each sheet.
2. Top each fillet with a teaspoon of capers. Pour over lemon juice and season with pepper to taste. Place two asparagus spears over each fillet and dust lightly with paprika.
3. Fold up edges of aluminum foil and completely encase fish. Place parcels on an oven tray and bake at 180°C/350°F/Gas 4 for 15-20 minutes, or until fish flakes when tested with a fork.