Cut the meat into 3 cm cubes. Peel and dice the onions. Heat the oil, roast the onions until light brown, add the paprika powder, stir, then deglaze immediately with a little cold water. Stir in the veal, sauté, season with salt. Pour hot stock, add lemon zest and juice. Cover the meat in the oven at 180 degrees for about 1 1/2 to 2 hours until soft.
Lift the meat out of the juice. Mix the sour cream and flour with a whisk and stir quickly into the boiling juice. Boil, season, mix or strain for 5 minutes.