Place half of the butter and the oil in a heavy skillet and sauté the garlic and onion in it until tender but not browned.
Add the tomato paste, tomatoes and salt and pepper to taste. Bring to a boil and simmer, uncovered, for twenty minutes. Force through a food mill or strainer. Add the orégano.
Cook the noodles until barely tender and drain.
Mix the noodles with the mozzarella cheese and the remaining butter. Place in the bottom of a buttered casserole. Pour the sauce over the top and sprinkle with the Parmesan cheese. Bake for fifteen to twenty minutes, or until the dish is bubbly hot.