Peel and finely chop the onion. Coarsely chop the bread and grind finely in the universal chopper. Whisk the egg. Knead minced meat, 100 g tomatoes, egg, 1 1/2 teaspoon salt, pepper and breadcrumbs and shape into an oblong meatloaf.
Place the roast in a large casserole dish. Cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 hour. Mix the rest tomatoes, mustard, vinegar, 250 ml (1 cup) water and sugar.
Pour about half of the sauce over the roast and continue cooking. About 20 minutes before the end of the cooking time, pour the remaining sauce over the roast. Prepare noodles in boiling salted water according to instructions on the packet.
Wash parsley, dab dry, pluck leaves from the stalks and cut into strips. Drain the pasta and let it drain. Remove the roast, cut into slices and arrange on plates with sauce and noodles.
Sprinkle with parsley.