1. Melt the butter over medium-low heat in a heavy bottomed 2-quart saucepan. Add the onions and cook until golden, about 5 to 10 minutes. Add the wine, tomatoes, and garlic. Bring to a boil, reduce heat to low, and cook 10 to 15 minutes, until a thick sauce forms.
2. Stir in the beans, season with salt and pepper, cover, and simmer for 15 minutes. Sprinkle with parsley.