1/4 c. butter
4 c. onion, thinly sliced
4 cans condensed beef broth, undiluted
1 tsp. salt
6 slices French bread, 1 inch thick
2 tbsp. grated Parmesan cheese
2 (1 oz.) pkgs. process Gruyere cheese, grated

In hot batter in large kettle, saute onion until golden brown, 8 minutes approximately. Add beef broth and salt, bring to a boil. Reduce heat and simmer, covered 30 minutes. Meanwhile, toast bread on both sides in broiler. Sprinkle one side with Parmesan and Gruyere cheese, broil just until cheese is bubbly, approximately 1 minute. To serve, pour soup into tureen or individual soup bowls. Float toast, cheese side up on soup.