Swordfish with Tomatoes and Capers

Name: Swordfish with Tomatoes and Capers
Ingredients: 1 cup chopped yellow onion (1 onion); 1 cup chopped fennel (1 bulb); 3 tablespoons good olive oil; 1 teaspoon minced garlic; 28 ounces canned plum tomatoes, drained; 1 teaspoon kosher salt; 3/4 teaspoon freshly ground black pepper; 2 tablespoons chicken stock; 2 tablespoons good dry white wine; 1/2 cup chopped fresh basil leaves; 2 tablespoons capers, drained; 1 tablespoon unsalted butter; 4 (1-inch-thick) swordfish fillets (about 2 1/2 pounds); Fresh basil leaves