Combine the tomatoes and 1 tablespoon olive oil in a small bowl, then set aside at room temperature for 5-10 minutes.
Rub both sides of each slice of bread with the raw garlic clove. Toast on the grill for 2-3 minutes on each side, or until golden brown and lightly crispy. Alternatively, you can toast in a toaster or using the oven broiler.
Add the fresh basil and (optional) balsamic vinegar to the tomatoes, carefully toss together, then add a generous scoop onto each toasted slice of bread. Garnish with flaky sea salt to serve immediately.