Marielle s French Onion Soup

¼ cup butter

2 large red onions, thinly sliced

2 tablespoons all-purpose flour

2 (10.5 ounce) cans beef broth

2 ½ cups water

6 slices French bread, toasted

½ cup grated Parmesan cheese

½ cup shredded Swiss cheese

Preheat an oven to 425 degrees F (220 degrees C).

Heat the butter in a skillet over medium heat. Stir in the onion; cook and stir until the onion has softened and turned translucent, about 5 minutes. Reduce heat to medium-low, and continue cooking and stirring until the onion is very tender and dark brown, 15 to 20 minutes more. Stir in the flour; cook and stir for a few minutes, then gradually add the beef broth and water. Bring to a boil, then simmer for 20 minutes.

Arrange French bread slices on a baking sheet, and sprinkle with Parmesan and Swiss cheese.

Bake in the preheated oven until the cheese is lightly browned and melted, about 10 minutes. Divide the soup into 6 bowls, and top with the cheesy bread.