Sift the flour and salt together and rub in the butter and lard until the mixture resembles bread crumbs. Add the cheese and bind with a little cold water. Chill for 30 minutes and then roll out to line an 8-inch flan dish. Chill again for 30 minutes.
Cover with foil and baking beans and bake blind in the oven for 10 minutes. Remove foil and baking beans and cook for a further 5 minutes. (If continuing with the recipe leave the oven on.)
For the filling:
Peel the tomatoes, seed, slice, strain and save the juice.
In a small pan heat the oil over a low heat and saute the onion until soft, add the garlic and oregano and cook for 1 minute. Add the tomato juice, season and cook until the juice is almost absorbed. Put this in the pastry case (shell) and cover with the fish. (If you are using fresh tuna cook it in a pan with a little more oil for about 2 minutes turning as necessary, then flake it.) Cover with the tomatoes and grated cheese. Whisk the eggs with the cream and pour over the tomatoes, scattering the olives on top. Bake in the oven for 15 to 20 minutes.
Serve hot or cold with a green salad, or a salad of green beans, or deep fried French Beans which you have dipped in batter