Cut meat into cubes. Mince onion, garlic and ginger finely. Heat some oil in a saucepan and fry onions till golden brown. Add garlic and ginger and fry well. Then add pepper, cummin and chili powder. Fry for five minutes and add meat. Fry the meat well till brown on all sides. Beat the yoghurt well with salt and add to the meat. Stir well and lower the heat and cook slowly till meat is tender. Add the lemon juice 10 minutes before the end of cooking time.