1. For the béchamel sauce, melt the butter in a saucepan. Add the flour and mix until smooth. Pour in the milk and broth, while stirring. Bring to a boil. Season with salt, pepper, and a little nutmeg in the sauce.
2. For the lasagna, slice the zucchini, dice the onions, and press the garlic. Heat 1 tsp of oil in a non-stick skillet. Sauté the zucchini slices for about 5 minutes. Season with salt and pepper, then remove from the skillet.
3. Sauté the diced onions and garlic in the cooking juice for about 3 minutes. Pour in the red wine. Add the tomatoes. Stir in the tuna. Season with salt, pepper, paprika, and chili powder.
4. Layer the lasagna sheets, tomato sauce, béchamel sauce, and zucchini slices in a gratin dish (24 cm x 28 cm). Finish with a layer of tomato sauce. Sprinkle the lasagna with grated cheese and bake in the middle of a preheated oven at 200 °C (gas mark 3, convection oven: 180 °C) for about 25 minutes. Sprinkle the lasagna with pine nuts. Serve garnished with basil.