Beef cut into pieces the size of small walnuts ( or slightly less)

Onions cut into rings.

Ceramic or glass dish for baking (with lid) grease with butter. ( Do not use enameled pots! I cook beef for this recipe in saucepan heat-resistant glass with a capacity of 2 liters. For meals, based on 1 kg of beef requires the capacity of 2-2.5 l). Spread in a greased bowl of meat and onions, stir, cover and put in a preheated 180 degrees oven. It is possible to forget about the meat for two hours! But I still recommend an hour to look under the cover. And if some pieces of meat will not be fully immersed in the selected juice, to help them - slightly press.

In a Cup of sour cream add a teaspoon of prepared mustard (I use Dijon, home cooked) and a teaspoon of flour. Mix well.

At the end of the allotted two hours, add to the meat the sour cream with the mustard and flour, stir, add salt and pepper to taste, cover and put into the oven for another half hour. And after half an hour of mouth-watering (and very tasty) beef, with a delicious onion sauce ready. Minimum effort for a very worthy dishes!