Melt butter in a Dutch oven over medium-high heat; add onion, and sauté 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.