Seed and finely dice the tomatoes, then place them in a medium bowl. Stir in the sliced basil, kosher salt, black pepper if using, and 1–2 tablespoons of the olive oil; add the balsamic vinegar only if desired.

Let the tomato mixture stand for 5–10 minutes so the seasoning can draw out the tomatoes’ flavor. Drain off excess liquid before topping the bread to help prevent soggy bruschetta.

Heat the oven to 400°F (200°C), or prepare a grill or grill pan. Lightly brush both sides of the bread slices with some of the remaining olive oil.

Toast the bread until crisp and lightly browned, about 5–8 minutes in the oven, turning once if needed. If using a grill or grill pan, cook the slices for 2–3 minutes per side.

While the toast is still warm, rub the cut sides of the garlic cloves directly over the surface of each slice. Use more or less garlic pressure depending on how pronounced you want the garlic flavor.

Spoon the drained tomato mixture over the warm toast immediately before serving. Finish each piece with a small drizzle of the remaining olive oil and serve right away.