Peel the onions and cut into fine strips. Then heat the margarine and sweat the onions in it. Fill up the broth and let everything cook for about 5 minutes. Season to taste with salt and pepper.
Divide the soup in soup cups and put 1 slice of toast in each cup. Sprinkle with some grated cheese.
Bake in a preheated oven at 150 ° C top / bottom heat for about 10 minutes. Serve immediately.