Boil the green beans for 10 – 15 minutes, season with salt and a pinch of pepper. Preheat the oven to 180°C.
Cut off the tops of the tomatoes and set aside. Then scoop out the tomatoes and keep the pulp. Place the tomatoes in a baking dish.
For the filling, finely chop the onion and garlic and fry in a little olive oil for about 5 minutes. Add the tomato pulp, then the chopped green beans, season with salt, pepper and oregano. Turn off the heat and mix with the tuna.
Fill the tomatoes with the filling, add the parmesan cheese and cover with the “tomato lids” set aside earlier.
Bake in the oven for about 10-15 minutes at medium heat.