How to Make It
Melt butter in a large Dutch oven over medium-high heat. Add onions, and sauté 20 to 24 minutes or until onions begin to caramelize and are very tender. Sprinkle with 1 tablespoon flour, and stir gently. Remove from Dutch oven.
Toss beef in remaining 2 tablespoons flour. Cook beef in hot oil in Dutch oven over medium-high heat 6 to 8 minutes or until browned.
Add wine and broth, and stir to loosen particles from bottom of Dutch oven. Add onions and any accumulated juices to Dutch oven; bring to a boil. Cover, reduce heat to low, and simmer 30 minutes.
Meanwhile, preheat oven to 350°. Bake bread slices on a jelly-roll pan 8 to 10 minutes or until crispy and lightly toasted. Serve with soup.