Baked Risotto with Tuna

Name: Baked Risotto with Tuna
Ingredients: 2 tablespoons extra-virgin olive oil; 1 onion, finely chopped; 1 clove garlic, finely chopped, optional; 1 teaspoon sea salt; 1 cup arborio rice; 1 1/2 cups chicken stock or water; 1 (14-ounce) can crushed Roma or Plum tomatoes; 1 (6.4-ounce) can packed tuna in spring water, drained (recommended: Sirena); 3 zucchinis, thinly sliced; Freshly cracked black pepper; 2 tablespoons finely chopped fresh flat-leaf parsley; Parmesan, for garnish, optional