Barbecued Pulled Chicken with Marinated Cucumbers

Ingredients

• 1/4 cup light brown sugar
• 1 tablespoon chili powder
• 2 teaspoons ground cumin
• 1/2 teaspoon salt
• 1/2 teaspoon paprika
• 1/4 teaspoon black pepper
• 1 pound skinless boneless chicken breasts
• 2 teaspoons olive oil
• 1 cup thinly sliced onion
• 1 cup fat-free less-sodium chicken broth
• 1 tablespoon balsamic vinegar
• 1/4 cup cider vinegar
• 2 tablespoons light brown sugar
• 1/4 teaspoon salt
• 1 cucumber, peeled and sliced
• 4 (2 ounce) hamburger buns