Fry the tomatoes, garlic, and onions in 1 Tbsp butter until the onions are soft but not brown. Set aside.
In another pan, make a roux by melting 2 Tbsp butter and blending 1 Tbsp flour stirring continuously for about 2 minutes.
Slowly stir 4 cups of water, crab meat, fried tomato mixture, diced potatoes, vinegar, salt, pepper and parsley together.
Simmer for one hour until the potatoes and crab meat are tender. Serve hot.