Add mushrooms if desired. If tomatoes are very meaty and have little liquid when cut, add a little water. Cook covered on low heat to barely boil, stirring occasionally until tomatoes cook down and chucks begin to break up. Uncover and add a teaspoon of Worchester sauce, stir in well, and cook a bit longer. Stirring should break up the chunks.
Ingredients are approximate measure.
Vary according to personal taste and volume of tomatoes. The sauce can be made directly in the Dutch oven over a very slow fire but it is easier in a separate small sauce pan. While sauce is cooking, cut open top of pepper and wash out seeds. Slice cross ways to make pepper rings. Peel onion and slice crossways.