Peel and finely chop the onion. Heat 1 tsp. fat. Sauté onion in it. Deglaze with tomatoes and chop a little in the pot. Bring to the boil and simmer for 5-8 minutes. Season the sauce with salt and pepper
Drain the tuna and tear with a fork. Wash the apple, quarter and core it. Cut into fine cubes and immediately sprinkle with 2 tsp. lemon juice
Wash and clean the chicory and cut in half lengthwise. If necessary, cut out the stalk in a wedge shape. Heat 3 tsp. fat. Fry chicory for 1-2 minutes on each side. Season with salt and 1 tsp. lemon juice
Wash the chives and cut into small rolls. Add to the sauce with tuna, apple and possibly capers. Arrange chicory and sauce. Garnish with apple and parsley if desired. White bread goes well with it