Peel the tomatoes. Remove the cores. Quarter the tomatoes.
Heat the butter in a saucepan and cook the onions and garlic in it until onions are translucent. Add the tomatoes and seasonings and cook for fifteen minutes, stirring occasionally. The tomatoes should retain some of their texture.
Strain the liquid from the tomatoes into another saucepan and reduce by half over high heat. Add the tomato pulp and heat thoroughly.