Preheat oven to 375°F and cook pasta 2 minutes under the normal time, then drain and return to pot.
Stir in drained tuna, frozen green beans, canned tomatoes with juice, and 3/4 cup cheese, then dot with butter pieces.
Transfer to a baking dish and bake for 12 minutes until bubbling.
Top with remaining cheese and bake 2 more minutes until melted.
Photo: Abdul Raheem Kannath / Unsplash