Onions peel and in fine cubes cut. Heat butter in a pot. Sauté onions in it. Sprinkle with 1 tbsp. sugar and caramelise lightly. Sprinkle with curry and sauté briefly.
Stir in tomatoes and ketchup. Bring to the boil and simmer for about 15 minutes.
For the meatballs, knead the minced meat, egg, breadcrumbs and tomato paste. Season with salt and pepper. Form approx. 20 balls from it. Heat the oil in a pan. Fry the balls in it in 2 portions all around for about 6 minutes.
Cook the pasta in 3-4 l boiling salted water (approx. 1 teaspoon salt per litre) according to the instructions on the packet. Slice Parmesan cheese into thin shavings with a peeler.
Season the sauce with salt, pepper and vinegar. Heat meatballs briefly in the sauce. Drain the pasta, let it drain and put it back into the pot. Mix in the sauce together with the meatballs. Serve and sprinkle with parmesan.