Cook the pasta in 4-5 l boiling salted water (approx. 1 teaspoon salt per litre) according to package instructions.
Preheat oven (electric cooker: 175°C/circulating air: 150°C/gas: level 2). Grate cheese. Whisk eggs. Stir in milk and 1/3 cheese. Season with 1 1/2 tsp. salt, pepper and nutmeg.
Drain the pasta well and put it in a large greased casserole dish (approx. 2 l capacity). Pour egg milk over it and sprinkle with the rest of the cheese. Bake in a hot oven for about 1 hour. About 15 minutes before the end of the baking time, spread 2 tbsp. butter in flakes on top.
Peel and finely dice the onions and garlic. Heat 75 g butter in a pot. Sauté onions and garlic in it. Dust with flour and sauté until light brown. Stir in tomato paste and sweat it on.
Stir in 3/4 l water, strained tomatoes and cream. Bring to the boil while stirring and simmer for about 5 minutes. Season with salt, pepper, 1 pinch of sugar and possibly Tabasco. Serve casserole with tomato sauce.