1Toast coriander, cumin and pepper in a small dry skillet over medium heat, stirring, until aromatic, about 45 seconds. Transfer to a small bowl, add salt and set aside.
2Preheat broiler. Lightly oil a broiler rack or coat with cooking spray.
3Place chicken breasts between two pieces of plastic wrap; flatten the meat slightly with a rolling pin. Discard the plastic wrap. Brush both sides of the chicken with oil, then coat with the spice mixture and place on the prepared rack. Broil until the chicken is no longer pink in the center, 4 to 5 minutes per side.