In a large heavy skillet, saute onion in oil over medium-high heat until tender but not browned. Add tomatoes, tomato paste, water, pepper, basil, oregano, salt and garlic powder. Bring to a boil, reduce heat and simmer 1 and 1/2 hours. Just before needed, saute the shrimp in only as much butter as needed until barely tender. Add wine and cook over high heat until wine is almost evaporated. To serve, place cooked thin pasta on platter or pasta plate. Pour a little of the shrimp cooking liquid over and toss. (You can also do this on individual plates) Top with some of the sauce and then some of the shrimp.