Preheat oven to 220℃/430°F. Place a heatproof roasting pan over a medium heat on the stove. In a bowl, place chicken, garlic, and cumin, spray with olive oil and toss to combine. Cook the chicken in roasting pan for 1 minute each side, or until browned. Transfer chicken to a plate.
To the pan, add tomatoes, capsicum, cauliflower, and onion. Spray with olive oil and toss to combine. Cook in the oven for 10 minutes
Place chicken in top of veges in pan. Cook for a further 10 minutes, or until chicken is cooked through and vegetables are tender.