Peel and boil potatoes and mash them, add a quarter of the cheese to the mash potatoes and mix.
Drain and put tuna into a good size mixing bowl, add chopped onions and tom sauce and mix.
Put thin layer of potatoes on the bottom of your pie dish, then the tuna mix and the rest of the potatoes on the top. Finish with the cheese topping
the potatoes and cook untill cheese is golden brown on mid hot oven "about gas 4 or 5"
You can eat it on its own or the kids like it with beans, or with salad. What ever you like really
Hope you enjoy
PS.. I have added a tin of baked beans before the mash top layer and its lovely too