This sauce is best when tomatoes are in season, and the best tomatoes for any sauce are the Roma variety. Chop about six tomatoes roughly, and throw them into the microwave. Give the tomatoes a good sprinkle with your best olive oil. When the mix has started to bubble, add a few pinches of salt and a pour of good soy sauce. Slice some onions and toss them in. Chop as many chillies as you fancy. The more chillies you eat, the more you can stand. Add a branch of rosemary. Cook gently over a low heat until the tomatoes have all but disintegrated and the onions have softened. Towards the end of cooking add some slices of ginger. Remove, strain and whizz. This sauce goes particularly well with pork. Use it quickly, or put some in the freezer. You can use it to add flavour to a wimpish soup.