Bring a pan of water to boil and add macaroni. Cook according to packet instructions.
Put oil and flour into another pan and make a paste. Cooking over medium heat, make sure that the flour cooks but doesn't burn; it should froth slightly.
Add the garlic puree to taste and then the juice from the tinned tomatoes (if you use chopped tomatoes you may have to add water and tomato puree). As soon as it thickens add tomatoes from the tin and stir in grated cheese (reserve a little of the cheese). Add water if sauce consistency is too thick until you have a nice coating consistency.
Check pasta; you can set sauce aside if pasta is not yet ready. Drain pasta as soon as it is ready and place in an oven dish. Top with remaining cheese (and sliced tomatoes). Place in oven or under grill till cheese topping browns. Serve with fresh bread.
Cheddar is a good choice, but almost any cheese can be used. Variations include adding ham or onion.