- 1 onion
- 2 tomatoes
- 1½ pounds kale or 1 package (10 ounces) frozen chopped spinach, thawed
- 1 cup fresh parsley leaves
- 8 tiny cornichons or ½ cup chopped nonsweet pickles
- 2 tablespoons olive oil
- ¼ cup dry white wine
- 1 tablespoon capers
- Salt and freshly ground black pepper
- 1½ pounds fresh tuna, sword fish, or halibut steaks
- Preheat the oven to 375°F.
- Finely chop the onion. Quarter the tomatoes, remove the seeds with a small spoon, and cut the pulp into ½-inch chunks. Stem, rinse, and chop the kale. Rinse and mince the parsley. Thinly slice or chop the cornichons.
- Heat the olive oil in a large ovenproof skillet over medium heat. Add the onion and sauté until tender, about 5 minutes.
- Add the white wine and simmer 2 to 3 minutes. Stir in the tomatoes, pickles, capers, and kale. Cover and simmer over low heat until the kale is tender, about 15 minutes. Uncover the skillet and season the vegetables to taste with salt and pepper.
- Set the tuna over the vegetables. Cover and bake until the tuna is nearly cooked through with traces of red or pink in the center, 10 to 15 minutes. (If the tuna is cooked all the way through, it will be too dry.) Serve hot.