Wash the roast beef and pat dry. Remove skin and tendons from meat with a sharp knife. Cut the upper layer of fat with the knife in a diamond shape. (Caution! Do not cut into the meat, otherwise too much juice will leak out.) Rub the meat with salt and pepper vigorously.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2). Heat lard in a roaster. Fry the roast beef on all sides over a high heat for 5-6 minutes.
Place the roaster in the oven with the layer of fat facing upwards. Insert a roast thermometer into the thickest part of the meat. Fry roast beef open for 35-40 minutes.
Cover meat several times with frying fat. At a core temperature of 55-65 °C the meat has a thoroughly pink-coloured core. Then remove and wrap in aluminium foil. Let it rest for at least 30 minutes so that it does not lose so much juice when cut.
In the meantime, boil eggs hard for the tartar sauce. Quench and let them cool down. Peel and finely dice onion. Dice cucumbers. Wash herbs and chop finely. Mix with salad cream, sour cream and cucumber water.
Dice eggs. Stir the cucumber and eggs into the cream. Season to taste with salt and pepper.
Cut the roast beef with a knife across the fibre into thin slices and serve with remoulade. Fried potatoes taste good with it.