Panzanella Caprese

1 (18-inch) piece of baguette, cut into 1-inch pieces
1/3 cup plus 2 Tbsp extra-virgin olive oil, divided
1 garlic clove
3 tablespoons balsamic vinegar
3 tablespoons drained capers, chopped
1 1/2 lb tomatoes, cut into 1-inch pieces
1 small red onion, thinly sliced
1 lb fresh mozzarella, cut into 1-inch chunks
1/2 cup chopped basil

Preheat oven to 375°F with rack in middle. Toss bread with 2 Tbsp oil and 1/4 tsp each of salt and pepper in a large 4-sided sheet pan, then spread out in 1 layer. Bake, stirring once, until golden, 12 to 15 minutes. Mince and mash garlic to a paste with 1/2 tsp salt. Transfer to a large bowl and whisk in vinegar, capers, and remaining 1/3 cup oil. Add croutons to dressing along with tomatoes, onion, mozzarella, and basil, then toss. Let stand at room temperature 30 minutes before serving.
    *Salad can be made 3 hours ahead and chilled. Bring to room temperature before serving.