Crispy Chicken Cutlets with Cherry Tomato Panzanella

Combine onion and 2 tablespoons vinegar in a small bowl. Season with salt and pepper; set aside.

Heat 2 tablespoons olive oil in a large skillet over medium-high. Add bread; season with salt and pepper. Cook, tossing, until golden brown, 5–8 minutes. Transfer to a medium bowl. Wipe out skillet.

Using a thin, sharp knife, cut bones and cartilage from chicken breasts. Pound chicken between 2 sheets of plastic wrap to 1/4" thick; season with salt and pepper.