Puree the tomatoes, onions and Scotch Bonnet peppers in a food processor. Transfer to a large saucepan and add the brown sugar, salt and vinegar; stir well to combine. Cook the sauce over medium heat, stirring occasionally, until it begins to boil. Lower the heat and simmer the sauce for 20 minutes, continuing to stir occasionally. Bottle the sauce in hot sterilized jars.
