Peel and finely chop the onion. Heat 1 teaspoon of fat. Sauté diced onion in it. Deglaze with 1/4 litre water. Add the contents of the package to the tomato sauce while stirring and bring to the boil.
Drain the tuna and cut it into small pieces. Wash and quarter the apple and remove the core. Dice the apple quarters. Wash the chives and cut into fine rolls. Add tuna, apple, chives and capers to the sauce.
Season to taste with salt and pepper. Clean and wash the chicory and cut it in half lengthwise. Cut out the stalk. Heat the remaining fat. Fry the chicory for about 2 minutes on each side.
Season with salt and lemon juice and serve with the sauce. Garnish as desired with apple slices and parsley. Baguette tastes good with it.