Bring a pot of salted water to the boil and add one tablespoon of the olive oil. Add the lentils and bay leaf and cook for 15 minutes, or until the lentils are tender. Drain well and set aside.
Heat the remaining oil in a frying pan and fry the onion for 5-6 minutes, or until the onion is soft and golden. Stir in the chopped chilli and cook for a further 1-2 minutes, then add the drained lentils and the tinned tomatoes with all of their juice. Season with salt and freshly ground black pepper, then lower the heat and allow to simmer gently for ten minutes.