Balsamic Chicken With Watercress and Nectarine Salad - Ellie Krieger

Ingredients

• 4 boneless, skinless chicken breast halves (1 1/4 pounds total), tenderloins and visible fat removed
• 3 tablespoons extra-virgin olive oil
• 2 teaspoons balsamic vinegar
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 3 to 3 1/2 ounces (1 bunch) fresh watercress, tough stems removed, coarsely chopped (about 2 1/2 cups lightly packed)
• 1 medium ripe nectarine, pitted and sliced into thin wedges
• 1/2 small red onion, sliced into thin half-moons