Sopa de Cebolla BlancaBellinghausen Restaurant in Mexico City, with a German name and Mexican ownership, has been in business for more than forty years, and serves many Mexican specialties. About the only German touch is draft beer—not unusual, since German played a role in teaching Mexico to make beer. Bellinghausen is one of my favorite places for lunch and people watching. Our favorite spot is the garden patio in the back, and I almost always order the wonderful onion soup made with white onions. This is my version of the soup.
Then, in a large saucepan, melt the butter over medium-low heat, and cook the onions, partially covered, stirring occasionally, until very tender and fragrant, but not brown, about 15 minutes.
Stir in the salt, pepper, and chicken stock.
Bring the soup to a boil, and cook 4 to 5 minutes to blend the flavors.
Serve the soup hot.
Pass the cheese, cilantro, and limes to add at the table.