In France they call it "Soupe à l'oignon". I'm not sure if my way is entirely French, but EVERYBODY that tried it absolutely loved it to bits.
Ingredients (serves 6):
3 big brown onions, cut in quarters, then in thick slices
3 big red onions, cut in halves (they are not as big), then in thick slices
2 slugs of olive oil
1 Lit beef broth (it's essential here it's made only with beef)
1 baguette, sliced
250gr gruviere cheese, grated (or mature red cheddar, but it's not the same thing)
2 cloves of garlic
You will need:
6 oven proof serving bowls
Method:
Prep your onions, then stir fry them in a heavy based big pot (I use a big wok for this), keeping them stewed under the lid until translucent
Remove the lid an dlet them brown
Add the broth, cover and let it simmer for 30 mins
Toast the bread or dry them toasting them in the oven at 200 degrees C
Brush the bread as soon as cool enough to handle with the cloves of garlic, on one side only, then set the bread into the bowls
Using a perforated ladle, spoon some of the onions on top of the bread in each bowl (not too many per bowl)
Add the broth, to each bowl, making sure that you leave 1cm from the top
Sprinkle the cheese on top, making sure it does not overflow (here I couldn't find gruviere, so it's red cheddar)
Bake in a pre-heated oven at 200 degrees C for 10 mins
WAIT at least 10 mins before serving (it'll still be super hot!)