Bonito and Tomato Soup, Basque style (Marmitako)

1 medium onion, finely chopped
5 tb olive oil
2 medium tomatoes, skinned, seeded and diced
1 tb minced parsley
1/2 tsp brandy or cognac
1/2 dried red chili pepper, seeds, removed, crushed
salt
ground pepper
3 garlic cloves, minced
2 medium potatoes, peeled and cubed
1 green pepper, minced
1 1/2 lbs. Fresh tuna (bonito) steaks

Saute 1 tb of the onion in 1 tb of the oil until wilted. Add tomatoes, parsley, brandy, chili pepper, salt and pepper. Cover and cook 20 minutes. Puree this mixture in a blender or processor, then thin with water to the consistency of tomato soup. Reserve. While the mixture is cooking, in a large, shallow casserole heat the remaining 4 tb of olive oil and saute the remaining onion and garlic in low heat, covered, until the onion is tender about 10 minutes. Stir in the potatoes and green pepper and cook 5 more minutes. Cover the potatoes with boiling water (about 1 1/2 cups), add salt and pepper. Return to a boil, add the fish, arranging it in 1 or 2 layers over the potatoes. When the fish turns white on both sides (about 5 minutes), remove to a warm platter while continuing to cook the potatoes until tender, 15 minutes or so. Cut the fish in chunks, removing skin and bones. Season with salt. Arrange fish over potatoes, then pour in the reserved tomato sauce. Stir gently and simmer 5 more minutes. Cover and let sit 5 minutes and serve, if possible, in the cooking dish. Eat with a crunchy bread and white wine.