PREPARATION

1. Check the green beans and boil them in plenty of boiling salted water for about 30 minutes.
2. Meanwhile, thinly slice the onion and fry it in a pan with a drizzle of olive oil; just browned, add tomatoes that you previously had cut into thin slices, season with salt and cook for 20 minutes stirring frequently.
3. Drain the beans and pour in a pan in which you have melted 2 tablespoons of butter, season with salt and add the bacon, cut into strips, stir often and cook for 10 minutes.
4. Put the tomatoes in a serving dish, cover with a layer of beans and bacon and finally pour the bechamel sauce warm.
5. Sprinkle with grated cheese and pepper and serve hot.