Rosemary chicken with tomato sauce

INGREDIENTS

• 1 tbsp olive oil
• 8 boneless, skinless chicken thighs
• 1 rosemary sprig, leaves finely chopped
• 1 red onion , finely sliced
• 3 garlic cloves , sliced
• 2 anchovy fillets, chopped
• 400g can chopped tomatoes
• 1 tbsp capers , drained
• 75ml red wine (optional)