Preheat the oven to 425°. Lay out four pieces of aluminum foil, about 1 foot wide.
Divide the fish and the shrimp among the four sheets of foil.
In a small bowl, combine the salt, paprika, and garlic powder. Season the seafood with this mixture. Season with pepper to taste. Divide the butter slices, onions, carrots, tomatoes, lemon slices, and dill sprigs among the four packets.
Fold the foil over the fish, bring the sides of the foil to meet in the middle. Fold the edges together several times in order to create a seal. Fold up the sides. Place the packets on a baking sheet. Bake for 10 to 15 minutes or until the fish pulls apart easily. Serve immediately.
Store leftovers in the fridge covered for up to 4 days.