Bring water to a boil, add salt, then add macaroni and leave boiling on light fire until half tender; drain water through a colander, add butter and start putting macaroni back into the pot in layers – layer of macaroni, some grated Parmesan and some vegetable sauce, macaroni again and so on until you run out of macaroni. Put the pot on the edge of the stove, cover with a lid and let it rest in light fire until the macaroni are soft and tender. Shake the pot occasionally to prevent them from burning.