Trim the French beans, once rinsed chop them and blanch them for 10 minutes in a pan with water and some salt then drain. Rinse the spinach and the Swiss chard, once drained chop them into thin strips. heat the oil in the saucepan, add the onion and the garlic and fry softly until golden.Add the strips of chard and the spinach and season with salt and pepper. Then add the French beans and the tomatoes. Mix well and simmer the sauce for 20 more minutes over a medium heat. Fold in the tuna, drained from the oil, 10 minutes before it is ready, mix well and flavour the sauce.Cook the pasta in plenty of boiling water, drain it al dente and toss it in the pan with the sauce, mix the ingredients well, sprinkle with parmesan and serve.