Carefully slice the breast almost in half horizontally, not quite cutting through to the other edge.
Keep that edge intact and open up the breast like you are opening up a book. This will make the meat a uniform thickness to ensure a quick and even cooking.
Heat a large saucepan over a medium-low heat. Add the olive oil to the pan. Once warm, add the peppers and chili flakes and cook for two minutes, then stir in the tomato purée and cook for two more minutes.
Add the passata to the pan, season with pepper, stir to mix well and reduce the heat to a gentle simmer. Leave to simmer gently while you prepare the rest of the dish.
Bring a large pan of salted water to the boil, add the gluten free pasta and cook according to the packet instructions. Add the zucchini three minutes before the end of cooking. Drain thoroughly.
Meanwhile heat a griddle pan over a high heat until smoking.
Rub the chicken with a little oil and season with a tiny bit of salt and pepper then griddle for 3-5 minutes on each side. Set aside to rest for five minutes before slicing into bite-sized pieces.
Add the cooked gluten free pasta and zucchini to the pan with the tomato sauce (if the sauce has thickened too much while simmering then add a little hot water from the pasta).
Stir to mix well and then add the cooked and sliced griddled chicken, spinach and the picked basil leaves (if using).
Season again with plenty of black pepper and allow the spinach and basil to wilt. Sprinkle with parmesan, if using, and serve.