Oven-baked chicken cacciatore

Name: Oven-baked chicken cacciatore
Prep time: 15 min
Cook time: 1 h
Total time: 1 h 15 min
Cuisine: European, Italian, Mediterranean
Ingredients: 2 onions (finely diced); 4 cloves garlic (finely chopped); 2 sticks celery (finely chopped); 4-6 chicken thigh fillets (skin removed and excess fat trimmed away); 1 red pepper (finely diced); 1 yellow pepper finely diced; 2 tins chopped tomatoes; 2 tbsp tomato puree; 2 tbsp Italian herb mix; 1 tbsp balsamic vinegar; large handful fresh parsley (finely chopped); salt and pepper; low calorie cooking spray or spray oil