Preheat barbecue on High and oil grate. Season chicken breasts and tomatoes. Reduce barbecue heat to medium and grill both chicken and tomatoes, around 7 minutes per side or until chicken juices run clear. (Remove tomatoes ahead of chicken if they collapse too much.)
Divide the salad between two dinner plates, then half-cover with arugula. Nicely arrange sliced chicken breasts and roasted tomatoes on top. Drizzle with hummus.