Preheat the oven to 200 degrees C (390 degrees F).
Combine the spice rub ingredients in a small bowl. Set aside.
Butterfly the chicken by cutting out the backbone (cut down each side of the bone to remove) and then place the chicken breast side up and flatten it with your hands.
Dry with paper towel and rub the spice mixture all over.
Heat an oven proof frying pan or dish on the stove over medium heat. Add 1 tablespoon of olive oil. Add the chicken breast side down and cook until just golden. Set the chicken aside on a plate.
Using the same frying pan with the heat off add the tomatoes, onion, garlic and extra olive oil. Season well with salt and pepper. Toss to coat.
Add chicken on top of the tomatoes and roast for 45 minutes. It is ready when inserted with a skewer the juices run clear.
Adapted from Curtis Stones book 'What's for dinner'