Put the butter and the onion in a 10-inch skillet, place over medium high heat and Sauté until it turns a rich golden color, about 5 minutes.
While the onion is Sautéing, remove the casing from the sausage and break it up into small pieces. When the onion is ready, add the sausage and cook until it has lightly browned. Add the tomatoes, season lightly with salt