Macaroni with ground beef

Ingredients:
Macaroni 400g(I used Penne Rigate)
200g ground beef
medium onion (chopped)
butter,sult,black pepper,1tbsp tomato paste
Put macaroni into boil water, add salt and 1tbsp vegetable oil.Macaroni boil until firm to the bite (stir frequently).In another pan roast ground beef and onion, add salt, black pepper, tomato paste. When macaroni is ready pour it's water and add prepared beef,2 tbsp butter and roast about 5 minutes.