In a large bowl, add tomatoes, avocado, lemon juice, basil, and garlic. Toss to combine. In a separate small bowl, whisk together balsamic vinegar, 1 tsp olive oil, sat, and pepper. Pour the dressing over the tomato mixture, tossing to coat.
Place toasted bread slices on a large platter. Top evenly with avocado tomato mixture. Garnish with freshly chopped basil and serve immediately.