Onion-Tomato Soup

2 large sweet Spanish onions (about 6 cups) sliced
1/2 cup butter
2-14.5 oz cans stewed tomatoes
3-14.5 oz cans beef broth
1/2 tsp basil
1/2 tsp salt
1/4 tsp pepper

Peel and slice onions thickly. Saute in butter in large saucepan. Add tomatoes, beef broth and spices. Cook over low heat for 45 minutes. Serve with toasted French bread.