Cook bacon and onion in a large dutch oven pot over medium heat 5 to 7 minutes. Add brown sugar, and cook, stirring occasionally, 1 to 2 minutes or until sugar is dissolved.
Stir in butterbeans and butter until melted and beans are thoroughly coated. Stir in water. Bring to a boil over medium-high heat; reduce heat to low. Simmer, stirring occasionally, 2 hours or until beans are very tender and liquid is thickened and just below the top of the beans. Stir in salt & pepper. Serves 6-8