For the tuna lasagna, first cut the cleaned or peeled vegetables into fine strips or cubes, finely dice the onion and garlic. Chop the tomatoes. Drain the tuna and also “pluck” or crush it very finely. Finely chop the herbs and capers.
Heat olive oil in a saucepan and sauté onions until light. Add garlic, celery and carrot strips and sauté. Add tuna with zucchini cubes and sauté. Deglaze with white wine and let it boil away. Add tomato paste, anchovy paste and capers, boil down briefly and then stir in the tomatoes and their liquid. Season with salt, pepper and dried oregano (add fresh herbs later!) and let everything boil down to a creamy sauce. Meanwhile, stir from time to time and add a little water or wine if needed. In the end, the sauce should be quite thick. Finally, stir in the herbs.
For the béchamel sauce, melt the butter, stir in the flour and cook briefly, stirring vigorously. Gradually pour in enough milk and/or soup to make a thick sauce. Keep stirring so that the sauce does not stick. Season and remove from heat.
Pour some tuna sauce into a suitable casserole dish lined with oil, place lasagna sheets on top and cover again with tuna sauce. Pour on some bechamel sauce, spread evenly and continue until all is used up.