Poached Cod in Spiced Tomato Sauce

Name: Poached Cod in Spiced Tomato Sauce
Prep time: 20 min
Cook time: 35 min
Total time: 55 min
Cuisine: American, Italian
Ingredients: 1 small orange; 1 leek (or 1 fennel bulb); 2 tablespoons extra-virgin olive oil; 1/4 teaspoon red pepper flakes (use 1/2 teaspoon for a spicier sauce); 3/4 teaspoon fennel seeds; 4 garlic cloves (thinly sliced); 1 small onion (finely diced); Salt and black pepper; 3 tablespoons tomato paste; 1/4 cup dry white wine (such as Chardonnay, Pinot Grigio, or Sauvignon Blanc); 1 teaspoon fish sauce (optional); 1 1/2 cups water; 2 tablespoons unsalted butter; 2 (6-ounce) cod fillets (ideally about 1/3-inch to 1/2-inch thick | or halibut or red snapper); 2 tablespoons Greek yogurt or creme fraiche (for serving | optional, for a creamy texture); A handful of flat-leaf parsley (finely chopped); Crusty bread (for serving)