Cut each chicken breast into small bite-sized pieces.
Combine the yogurt, curry, lemon juice, and salt. Mix, and marinate the chicken in this mixture for one hour or longer.
Thread on skewers, with onions and tomatoes in between every two or so chicken pieces.
Broil over charcoal or in your oven broiler, turning until chicken is cooked (about 10 minutes) and basting with marinade. Garnish with melon slices or grapes.