It is necessary:
50 g butter,
2 head finely chopped onion
2 peeled and finely sliced tomatoes,
500 g cooked ground beef,
500 g mashed potato
50 g grated Parmesan cheese.
Sauté onion in butter.
Add tomatoes and meat, season with salt and pepper and stir well.
Cover bottom of greased casserole with a half of puree.
Over it distribute the meat from the top to put the remaining puree.
Sprinkle grated cheese and bake in preheated oven at 250 ⁰ C until potatoes browned.