Trim the pork fillets of any fat or sinew. Cut into slices 3 cm thick. Put the flour into a big mixing bowl and season it generously with salt and milled black pepper.
Heat a large frying pan and add the oil and butter. While the fat is heating, put the fillet slices into the bowl of seasoned flour and toss them around so they're well coated. Pat and shake the slices energetically to remove the excess flour - they should be just lightly dusted. When the fat is very hot, brown the slices on both sides (in two or three batches, and without overcrowding the pan) until they have a nice golden crust, but are still somewhat raw on the inside. Set each batch aside on a plate while you finish frying the rest.
Remove the pork, then brown the onions. Once the onions are done add the pork, tomato paste, garlic, paprika, lemon juice, wine and sugar. and cook until the pork is done.
Add the yogurt and parsley and heat through. Serve on rice.
You can add chopped cauliflower, green beans, peppers, etc if you desire.