Cut the blanched tripe into slices, and dredge well with flour seasoned with oregano.
Melt the butter in the casserole in which the dish will be served.
Put in the floured tripe, and let it cook gently for about 10 minutes.
Add the sliced onions and the crushed clove of garlic.
Thicken with the flour and tomato puree, smoothing out any lumps, and add gently the stock or water.
Season with salt and cayenne to taste.
Cover and cook in a slow oven for 2 1/2-3 hours.