Crush onions and garlic and fry in olive oil, seasoned with salt and oregano. Add tomato paste and cook for 5 minutes. Then put the grated tomatoes and bring to a boil, stirring occasionally. Reduce the heat and cook the sauce for an hour, stirring every 5 minutes so that it does not burn.
In the meantime, mix all the ingredients for the meatballs , except the butter. Form small balls from the resulting mixture and place them on a greased baking dish. Place in preheated oven at 230 ° C for 20 minutes. Pour tomato sauce over meatballs and bake for another 15 minutes.