Soak the cod in water overnight to remove salt. Heat olive oil in a saucepan and roast the onions. Add dill, parsley, spinach and lettuce and roast them for a while. Dredge oregano over them and add the cod. Dissolve the tomato paste into a glass of water and pour it over the cod. Let the cod simmer for 30 minutes. Do not stir during these period.