Bring to the boil a large pan of salted water. Cook the spaghetti in the boiling water, following the instructions on the packet for timing.
Heat the olive oil in a saucepan and fry the onion and garlic for five minutes. Add the chopped chilli and halved tomatoes. Cook, stirring, on a medium-low heat for two minutes.
Add half the torn basil and the squid. Cook over a low heat for 5-10 minutes, or until the squid flesh is cooked but still tender.
Drain the spaghetti and mix with the sauce in the pan. Season with salt and freshly ground black pepper, to taste.
To serve, put the spaghetti in a bowl, scatter over the rest of the torn basil and serve with a lemon wedge.
