Braised Cod with Summer Vegetables

Name: Braised Cod with Summer Vegetables
Ingredients: 2 Tablespoons extra virgin olive oil; 3/4 cup thinly sliced onion, (yield of about one medium); 3/4 pound fresh or frozen defrosted cod fillet,, cut into large chunks, if desired (optional; you can leave as fillets); 1 cup unsalted tomato puree; 1 medium tomato,, diced; 1 large red pepper,, seeds and stem discarded and diced; 1 large zucchini,, stem discarded, diced (no need to peel); 1-2 Tablespoons freshly squeezed lemon juice, (to taste); 2 Tablespoons fresh tarragon leaves; 1/4 teaspoon ground black pepper,, or to taste; 1/8 teaspoon fine sea salt,, or to taste