What ingredient is primarily responsible for the savory flavor of a traditional Quiche Lorraine?

In a traditional Quiche Lorraine, the primary ingredient that lends its characteristic savory flavor is bacon. Quiche Lorraine originated from the Lorraine region of France, where it was traditionally made with a custard filling that includes eggs and cream, but the inclusion of bacon is what defines this particular quiche and gives it its distinctive taste. The smoky, salty quality of the bacon enhances the overall flavor profile, making it rich and savory.

While eggs and cheese contribute to the texture and richness of the quiche, and onion adds some aromatic depth, it is the bacon that stands out as the key ingredient that provides that unique savory element associated with this dish. The fatty, umami characteristics of the bacon are what truly elevate the quiche, making it more than just a simple egg custard.