Ingredients

1. 1/3 cup plus 1/4 cup extra-virgin olive oil
2. 1 large onion plus 1 small onion, finely chopped
3. 1/4 pound prosciutto, sliced 1/4-inch thick and cut into 1/2 -inch dice
4. 3 large shallots, finely chopped
5. 6 thyme sprigs
6. 4 large garlic cloves, minced
7. 3 bay leaves
8. 3 large red bell peppers, cut into 1/2 -inch dice
9. 2 medium yellow bell peppers, cut into 1/2 -inch dice
10. 1 medium eggplant, peeled and cut into 1/2 -inch dice
11. 2 pounds zucchini, cut into 1/2 -inch dice
12. 1 cup dry white wine
13. 4 medium tomatoes--peeled, seeded and coarsely chopped
14. 1 1/2 cups V-8 juice
15. 1/2 tablespoon tomato paste
16. Salt and freshly ground pepper
17. Four 1 3/4-inch-thick tuna steaks (about 1 1/4 pounds each) 

Directions

1. Heat 1/3 cup of the olive oil in a large enameled cast-iron casserole. Add the onions, prosciutto, shallots, thyme, garlic and bay leaves and cook over moderately low heat, stirring, until the onions begin to soften, about 5 minutes. Reduce the heat to low and cook until softened, about 12 minutes.
2. Add the bell peppers and cook until softened, about 5 minutes. Add the eggplant and cook until softened, about 5 minutes. Add the zucchini and cook, stirring often, until softened, about 10 minutes. Add the wine and simmer over moderately high heat for 5 minutes. Add the tomatoes and simmer for 5 minutes longer, then add the V-8 juice and tomato paste. Simmer over moderate heat until thickened, about 15 minutes. Discard the thyme and bay leaves and season with salt and pepper.
3. Preheat the oven to 425°. Heat 2 large ovenproof skillets. Season the tuna steaks with salt and pepper. Add 2 tablespoons of the olive oil to each skillet. When the oil shimmers, add 2 tuna steaks to each skillet and cook over high heat until deeply browned on the bottom, about 4 minutes. Turn the steaks over and transfer the skillets to the oven. Roast for about 8 minutes, or until the tuna is pink inside. Transfer the tuna steaks to a carving board.
4. Ladle the sauce onto 2 large platters. Slice the tuna across the grain 1/2 -inch thick. Arrange the tuna on the sauce, pour the pan juices over the tuna and serve very warm but not steaming hot.

Make Ahead

The vegetable Basquaise can be refrigerated for up to 1 day. Reheat before serving.