Wash the meat, dab dry and cut into strips. Heat oil in a pan. Fry the meat for about 5 minutes. Season with salt and pepper and remove. Cook pasta in 3-4 l boiling salted water according to package instructions.
In the meantime peel and finely dice the onions. Grate cheese. Heat 1 tablespoon butter in a large pot. Fry the onions in it until transparent. Dust with flour and sweat lightly. Deglaze with milk, bring to the boil while stirring continuously and simmer for 2-3 minutes.
Stir in cheese, up to 3 tablespoons, and tomato paste and simmer until the cheese has melted. Season sauce with salt, pepper and vinegar.
Drain pasta well and mix with meat and sauce. Put them in four small or one large greased casserole dish. Crumble the pretzel finely. Knead with remaining cheese and 2 tablespoons butter and spread as flakes on the noodles.
Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for approx. 20 minutes.