In a large bowl, soak potato cubes in cold water.
Sprinkle tuna evenly with salt and Adobo. In a large saucepan or soup pot, lightly sauté tuna in olive oil; remove tuna and set aside.
In same pan, sauté onion until soft. Add green pepper, garlic, bay leaf, drained potato cubes, and white wine. Bring to a boil, reduce heat and simmer, uncovered, for 2-3 minutes.
Add fish stock and simmer, covered, for 10 minutes or until potatoes are tender. Add tuna and pimientos to stew and simmer, covered, for an additional 3-4 minutes.
Remove bay leaf. Salt to taste. Garnish with parsley.