Mediterranean Grilled Tuna Sandwich

Name: Mediterranean Grilled Tuna Sandwich
Prep time: 30 min
Total time: 30 min
Cuisine: Mediterranean
Ingredients: 1/4 cup olive or vegetable oil; 1 tablespoon chopped fresh or 1 teaspoon dried thyme leaves; 1 tablespoon red wine vinegar; 1/4 teaspoon salt; Dash of pepper; 1 clove garlic, finely chopped; 1/2 pound tuna, or marlin fillets, 3/4 to 1 inch thick; 1 medium tomato, seeded and coarsely chopped (3/4 cup); 1/4 medium red onion, thinly sliced; 2 tablespoons chopped pitted kalamata or ripe olives; 2 tablespoons chopped fresh Italian or regular parsley; 2 teaspoons capers; 1 loaf (1/2 pound) unsliced crusty Italian, French or sourdough bread; 2 leaves romaine lettuce, shredded