Season fish with salt and set aside. In a saucepan, bring water and wine to a boil. Turn heat down to medium-low and add onions, carrots, potatoes, parsley, and peppercorns. Cook, uncovered, until potatoes are tender, about 30 minutes.
Pour contents of saucepan through a fine mesh strainer set over a skillet large enough to fit the fish pieces. Remove potatoes from strainer and keep warm in a covered bowl.
Place turbot pieces in the sauté pan with strained broth. Bring to a boil over medium heat, then decrease the heat and simmer over low heat, uncovered, until fish becomes opaque. About 10 minutes.
While fish is cooking, heat olive oil over high heat in another frying pan. Add garlic, onion, bay leaf and cook, stirring, for around 10 minutes or until onion turns golden brown. Remove from heat and add lemon and paprika, mix well. Season to taste with salt and pepper.
Divide fish and potatoes between plates, pour sauce over fish and serve while hot.