Melt butter in a Dutch oven over medium-high heat; add onion, and saut 8 minutes or until tender. Stir in soup, and bring to a boil. Stir in beans and next 3 ingredients. Spoon into a lightly greased 13- x 9-inch baking dish.
Sprinkle evenly with shredded Cheddar cheese.
Bake, covered, at 375 for 25 minutes. Uncover and sprinkle evenly with French fried onions, and bake 10 more minutes or until bubbly.