Pat the meat dry with kitchen paper towels. Peel apples, remove the cores, and cut in slices. Melt butter in a pan; brown apples for about 3 minutes on each side until light brown. Remove from pan and keep warm. Flour liver carefully. Heat oil in a second pan; brown liver for 4 minutes from each side and season with salt. Mix flour and paprika, stir in onion cut into rings and bake in a pot with oil at 180° C until golden brown. Serve on a preheated plate. Garnish with apple slices and onion. Add chopped parsley to the remaining meat juice and pour over meat. Serve immediately to avoid the liver from getting tough.