Preheat oven to 350°F. In a large saucepan, scald milk, nutmeg, chili flakes, celery seed and dry mustard. In a separate saucepan, render the bacon over low heat until it appears no more fat will release. Turn the heat to medium and cook the bacon until it becomes somewhat crisp. Add the flour to the bacon and mix thoroughly with a wooden spoon. Turn off the heat and add the milk mixture a little at a time, mixing thoroughly with a whisk until smooth after each addition (this will avoid lumps in the sauce). Once all the milk has been added and the sauce is smooth, add the 4 cups of cheese and mix well. Add the macaroni and tomato, mix well and pour into a greased 9"x 13" casserole dish. Top with the additional cheese and then breadcrumbs. Bake for about 30 minutes, or until sauce is bubbly and the crumbs are golden brown.