In a medium bowl, mix together the tomatoes, grated garlic, vinegar, salt, and several grinds of pepper. Stir in the olives and capers, if using.
Drizzle the bread slices with olive oil and grill until lightly charred, or toast in the oven. Use the cut-side of the garlic halves to rub garlic onto the hot bread. Top with the tomato mixture and fresh basil.