Beef stroganoff

Ingredients:

500 g beef (tenderloin or fillet)
1 large onion
200 g sour cream
2 tbsp. flour
2 tbsp. tomato paste
100 ml of beef broth
Salt and pepper to taste
2 tbsp. vegetable oil
Preparation:

Slice the beef into thin strips across the fibres.
Peel the onion and cut into small cubes.
Heat the vegetable oil in a frying pan and fry the onion until golden.
Add the meat and fry over a high heat until browned.
Sprinkle with flour and stir well.
Add the tomato paste and cook for a further 2-3 minutes.
Pour in the stock, add the sour cream, salt and pepper. Stir thoroughly.
Turn down the heat and simmer under a lid for 15-20 minutes until the meat is soft and the sauce has thickened.